A/C Compressor

[lindbergh]

Does anyone know the Sanden model number of the original, stock, R12 A/C Compressor (i.e. 505, 508 etc.). Thanks.

[ramblinmike]

Does anyone know the Sanden model number of the original, stock, R12 A/C Compressor (i.e. 505, 508 etc.). Thanks.

SD-510 I believe.

[Henrik]

The Delorean stock compressor is an SD-510Q8494 where :
- the 5 designates 5 cylinders
- the 10 stands for 10 cu in displacement per revolution
- Q is the type of cylinder head
- 8494 defines the combination of mounting, clutch size, offset, oil amount etc.
- this compressor used to be made at Sanden's old plant in Dallas, TX but is no longer in production (mostly because it was unable to withstand the higher pressures and loads/less efficient lubrication associated with R134a)

A perfect R134a drop-in replacement would be the Sanden SD7H15QC4708:
- the 7 designates 7 cylinders
- 15 stands for 155 cc displacement per revolution (about 9.5 cu in)
- this is a quieter, more durable compressor, specifically for R134a
- this compressor is produced in Wylie, TX
- I use this compressor on my D.

See attached drawings for both.

Henrik
former Application Engineer and Lab Manager at Sanden
1782917830

[BABIS]

The Delorean stock compressor is an SD-510Q8494 where :
- the 5 designates 5 cylinders
- the 10 stands for 10 cu in displacement per revolution
- Q is the type of cylinder head
- 8494 defines the combination of mounting, clutch size, offset, oil amount etc.
- this compressor used to be made at Sanden's old plant in Dallas, TX but is no longer in production (mostly because it was unable to withstand the higher pressures and loads/less efficient lubrication associated with R134a)

A perfect R134a drop-in replacement would be the Sanden SD7H15QC4708:
- the 7 designates 7 cylinders
- 15 stands for 155 cc displacement per revolution (about 9.5 cu in)
- this is a quieter, more durable compressor, specifically for R134a
- this compressor is produced in Wylie, TX
- I use this compressor on my D.

See attached drawings for both.

Henrik
former Application Engineer and Lab Manager at Sanden
1782917830


thanks for the usefull informations!

do you have some pictures of this compressor installed on your D?

thanks

[Ron]

See attached drawings for both.

:thumbup2:

(Copied (http://dmctalk.org/showthread.php?353-Sanden-SD-AC-Compressor-Service-Manual&p=97246&viewfull=1#post97246) to Resources)

[ramblinmike]

I just did a google search for this part number: SD7H15QC4708.

Came up with nothing. I then went to rockauto.com and tried to look this number up so I could see a price. Search came up empty. Any ideas where you can buy this compressor?

[Henrik]

thanks for the usefull informations!

do you have some pictures of this compressor installed on your D?

thanks

Go here http://public.fotki.com/henkan/delorean/ and scroll to the bottom.

[Henrik]

I just did a google search for this part number: SD7H15QC4708.

Came up with nothing. I then went to rockauto.com and tried to look this number up so I could see a price. Search came up empty. Any ideas where you can buy this compressor?

The SD lines of compressors are very end-user friendly in that it is modular, meaning that you can more or less “build” your own SD compressor using whatever clutch style, clutch diameter, clutch offset, clutch voltage, mounting type, oil amount, cylinder head, hose mounting style etc. With that you can imagine that the number of configurations is almost infinite. The combination of all of these options are defined by the last four digits, i.e. the 4708 in the case of the SD7H15. Over the years, Sanden has offered whatever combination of features the customers have required (assuming the sales volume was there) and then given it a four digit number. However, most aftermarket retailers and distributors may only have purchased certain models for specific car models and model years and/or some common config that would fit a lot of applications. Also, if you contact the retailers/distributors they are not going to know what a “4708” is. All they know is that a certain compressor will fit a 1998 Dodge Ram truck or whatever. The best chance of finding what you need is to go to a larger a/m company’s website such as Four Seasons (www.4s.com) and download their eCatalog. There are other, similar companies out there too. Google is your friend here. If you’re lucky then you may find a cross reference showing which xxxx model go on what model/make and then you may find it easier to look for that compressor in the a/m world. If none of that works, then you need to find a retailer that is willing to configure a compressor for you. I have the name of such a place at home; send me a PM and I can let you know who I contacted and what I asked for. This was 6-7 years ago so hopefully they’re still there… :smile:

[Henrik]

Actually, finding a 4708 is very easy:
Go to www.sanden.com. Select Products and Product Search. Under Sanden Model # enter: 4708. You can buy it right there.

[BABIS]

Actually, finding a 4708 is very easy:
Go to www.sanden.com. Select Products and Product Search. Under Sanden Model # enter: 4708. You can buy it right there.

many thanks.

I noticed that the sanden site says it needs 135 cc of oil, but I red in your blog that you put 240 cc, any opinion about this?

[Henrik]

many thanks.

I noticed that the sanden site says it needs 135 cc of oil, but I red in your blog that you put 240 cc, any opinion about this?

Yes, good catch. 135 cc is the standard amount and is sufficient for most smaller A/C systems that use a TXV (thermostatic expansion valve) in order to drop the pressure of the refrigerant. Our Ds, however, use a so called Orifice Tube system and the reason more oil is needed is that OT systems use a large accumulator on the low pressure side of the system that tend to trap a lot of excess oil (the low pressure, cold refrigerant in vapor state is unable to "flush" the oil out of the accumulator). So more oil is needed in order for the right amount to return to the compressor. (BTW, most compressors hold no oil while running but rely on a constant amount of oil circulating in the system; the oil is cooled as it passes through the evaporator)

You should be able to find Sanden SP-20 PAG oil or equivalent in the auto parts store. Maybe you can find it on Sanden.com.

[AdmiralSenn]

I am so glad you're here, Henrik, because I have questions!

What would be the designation for the SD710 series you suggested, but with a serpentine belt pulley? I believe I need a five groove.

And do you think it's feasible to switch to a different mounting style? I've been trying to figure out if I can somehow mount the compressor directly to the valve cover's upper surface. Not a big deal if I can't, but I'd like to free up some room in the spark plug/fuel injector area since my EFI injectors are slightly cramped.

Thanks!

[BABIS]

Yes, good catch. 135 cc is the standard amount and is sufficient for most smaller A/C systems that use a TXV (thermostatic expansion valve) in order to drop the pressure of the refrigerant. Our Ds, however, use a so called Orifice Tube system and the reason more oil is needed is that OT systems use a large accumulator on the low pressure side of the system that tend to trap a lot of excess oil (the low pressure, cold refrigerant in vapor state is unable to "flush" the oil out of the accumulator). So more oil is needed in order for the right amount to return to the compressor. (BTW, most compressors hold no oil while running but rely on a constant amount of oil circulating in the system; the oil is cooled as it passes through the evaporator)


Thanks for the explanation!



You should be able to find Sanden SP-20 PAG oil or equivalent in the auto parts store. Maybe you can find it on Sanden.com.

the right one should be the SP-15, or not?


anyway I found one on ebay http://www.ebay.com/itm/NEW-AC-COMPRESSOR-SANDEN-4708-SD7H15-/290690287980?pt=Motors_Car_Truck_Parts_Accessories&hash=item43ae7dc96c&vxp=mtr

[jawn101]

Thanks for the explanation!



the right one should be the SP-15, or not?


anyway I found one on ebay http://www.ebay.com/itm/NEW-AC-COMPRESSOR-SANDEN-4708-SD7H15-/290690287980?pt=Motors_Car_Truck_Parts_Accessories&hash=item43ae7dc96c&vxp=mtr

I'm sure Henrik will agree, be very careful with Sanden stuff off eBay - believe it or not, they are commonly faked!!

[Henrik]

I am so glad you're here, Henrik, because I have questions!

What would be the designation for the SD710 series you suggested, but with a serpentine belt pulley? I believe I need a five groove.

And do you think it's feasible to switch to a different mounting style? I've been trying to figure out if I can somehow mount the compressor directly to the valve cover's upper surface. Not a big deal if I can't, but I'd like to free up some room in the spark plug/fuel injector area since my EFI injectors are slightly cramped.

Thanks!

The SD7H15 (for R134a) used to be called SD-709 back during the R-12 era, so there never was an SD-710... Anyway, once you start to figure out what compressor configuration you need you need access to that long list of models. (There is no logic behind the four digit model number scheme by the way; it's totally arbitrary.) As mentioned earlier your best bet is to download the eCatalog from www.4s.com or someone similar. I may be able to get it from my old Sanden colleagues. Sure you can switch to a different mounting style but then you will of course need to design/make a bracket, find the correct belt length etc.

[Henrik]

the right one should be the SP-15, or not?

I think you're right: I little bit of history: In the 90s we developed the SD7 line piston compressors with the thicker SP-20 oil. At the same time, the TR scroll compressors were adapted for R134a with the thinner SP-10 oil. At some point a cost reduction program was started that concluded that both lines of compressors would actually pass the design specifications using a blend of SP-20 and SP-10. The new blend was called - you guessed it - SP-15.

[Henrik]

I'm sure Henrik will agree, be very careful with Sanden stuff off eBay - believe it or not, they are commonly faked!!

True. I have been to trade shows where Chinese companies were selling 100% perfect Sanden clones made in China. The only difference would be the name on the label that would be intentionally and very slightly mispelled so no one could accuse them for forgery.

[lindbergh]

Thanks Hendrik!

Another question

I would like to use R-12 (have several lbs. left) - can I use a R134 compressor with R12? and is there an oil compatibility issue?

Thanks.

[Henrik]

Thanks Hendrik!

Another question

I would like to use R-12 (have several lbs. left) - can I use a R134 compressor with R12? and is there an oil compatibility issue?

Thanks.

Yes, you can use an R134a compressor for R-12. But, I have honestly never encountered the scenario where a new R134compressor (with residual PAG oil in it) was installed on an existing R-12 system (that has mineral oil already in the system). The two oils are not compatible but have not been known to cause any durability issues when mixed. However, I don't know the PAG oil's effect on R-12.... Just make sure you remove as much of the PAG oil from the R134a compressor as you can before you install it and you should most likely be OK.

[lindbergh]

Yes, you can use an R134a compressor for R-12. But, I have honestly never encountered the scenario where a new R134compressor (with residual PAG oil in it) was installed on an existing R-12 system (that has mineral oil already in the system). The two oils are not compatible but have not been known to cause any durability issues when mixed. However, I don't know the PAG oil's effect on R-12.... Just make sure you remove as much of the PAG oil from the R134a compressor as you can before you install it and you should most likely be OK.

Thanks again Henrik, I appreciate all your help.

[SS Spoiler]

I say we make "Sir Henrik" permanent AC expert!!

[Henrik]

I say we make "Sir Henrik" permanent AC expert!!

:thankyou:

[Bitsyncmaster]

Yes, you can use an R134a compressor for R-12. But, I have honestly never encountered the scenario where a new R134compressor (with residual PAG oil in it) was installed on an existing R-12 system (that has mineral oil already in the system). The two oils are not compatible but have not been known to cause any durability issues when mixed. However, I don't know the PAG oil's effect on R-12.... Just make sure you remove as much of the PAG oil from the R134a compressor as you can before you install it and you should most likely be OK.

I seem to remember reading somewhere that any PAG oil will cause big problems with R12.

[kings1527]

Yes, you can use an R134a compressor for R-12. But, I have honestly never encountered the scenario where a new R134compressor (with residual PAG oil in it) was installed on an existing R-12 system (that has mineral oil already in the system). The two oils are not compatible but have not been known to cause any durability issues when mixed. However, I don't know the PAG oil's effect on R-12.... Just make sure you remove as much of the PAG oil from the R134a compressor as you can before you install it and you should most likely be OK.


I seem to remember reading somewhere that any PAG oil will cause big problems with R12.

I wonder if it's possible to have a compressor shipped directly from Sanden and specially request that it be filled with either mineral oil or no oil at all.

[Henrik]

I wonder if it's possible to have a compressor shipped directly from Sanden and specially request that it be filled with either mineral oil or no oil at all.

There is a Contact Us page on sanden.com so you can always ask them. I am surprised Sanden even take single orders straight off of their website though. In my days, 80s/90s, they wouldn't even bother with anyone who wasn't an already established distributor. As times have gotten tougher they didn't want to pass up any sales, I guess - and the web made it cost effective....

[kings1527]

Yes, you can use an R134a compressor for R-12. But, I have honestly never encountered the scenario where a new R134compressor (with residual PAG oil in it) was installed on an existing R-12 system (that has mineral oil already in the system). The two oils are not compatible but have not been known to cause any durability issues when mixed. However, I don't know the PAG oil's effect on R-12.... Just make sure you remove as much of the PAG oil from the R134a compressor as you can before you install it and you should most likely be OK.

Touching on this again for just a second. I'm curious about using an r134a compressor on my R12 system if need be but I'm wondering about being able to dial in pressures correctly since the displacement on the SD7H15 is slightly less compared to the stock SD-510 (9.5cc per revolution, versus 10cc on the 510).

Again, this would be a r134a compressor on an R12 system. Does that mean our cut in/cut out pressures will change due to the difference in displacement or am I overthinking this? For some reason, I'm thinking the difference in displacement is going to cause issues with operating pressures and therefore temperatures. And would that mean that the low pressure switch would need an adjustment?

Or maybe it's late and I should just go to bed...

[DMC5180]

It's late and you should be in bed :biggrin:

I had nice conversation with Henrik a while back. Super knowledgeable and helpful.

Henrik told me the SD7 series was developed to help reduce the Running Noise and reduce compressor load (more pistons) for the high operating pressures.

With the displacement variable being very minor in this case it should only mean the compressor will run slightly longer run for the given cycle. The compressor is just a pump. They should be now need to change any LOW side PSI settings.

I'm sure Henrik will clarify if I'm off base here. I don't know if their are any internal components that would not be compatible with mineral oil though.

[Henrik]

Yeah, Dennis is right. Think of the compressor as a pump that compresses and moves refrigerant in a vapor state.

A compressor can definitely be over/undersized for a given system but in this case the difference is insignificant. Actually, although the SD7 has a slightly lower physical displacement than the SD5, its volumetric efficiency is somewhat higher so the actual pumping capacity between the two are pretty much identical. This is of course assuming the same clutch diameter between the two.

[kings1527]

I figured as much, Dennis! I must still be dealing with that NYE party.... :drunk:

That makes total sense. Thanks guys. When the time comes, I'll try ordering a new SD7 compressor without any PAG or esther oil but if it still comes with it, I'll drain it and try pouring mineral oil in it and emptying it out again a few times. Trying to 'flush' out the other oil the best I can. My NOS SD-510 seems to have a clutch seal leak (very slight) so I'll get around to fixing it/replacing the compressor when the temps become noticeable. It's been nearly a year now and everything is still perfect so I have no idea when that'll be.

[David T]

I figured as much, Dennis! I must still be dealing with that NYE party.... :drunk:

That makes total sense. Thanks guys. When the time comes, I'll try ordering a new SD7 compressor without any PAG or esther oil but if it still comes with it, I'll drain it and try pouring mineral oil in it and emptying it out again a few times. Trying to 'flush' out the other oil the best I can. My NOS SD-510 seems to have a clutch seal leak (very slight) so I'll get around to fixing it/replacing the compressor when the temps become noticeable. It's been nearly a year now and everything is still perfect so I have no idea when that'll be.

There are a lot of subtle differences among the compressors. What it all comes down to is mounting lugs, clutch and backplate. In our system just about all of them will work if they fit. To use -134 you will need to adjust the low pressure switch a little higher because -134 operates at higher pressures. -134 also has a lower heat content so the same amount of -134 can carry a little bit less heat than the same amount of -12. To further add to the complications you can't out the same amount of -134 in as -12. Bottom-lining this, -134 operates at higher pressures than -12 and won't give you the same capacity as -12. All of this is assuming you are talking about the same system (a Delorean A/C). This is all because of the way the system was designed, for -12. On systems designed to use -134, the evap coil and the condenser coil are made bigger to achieve the same cooling capacity as -12. If all you have is a seal leak it is an easy fix. If you don't want to do it there are places you can send it out to that can do it. It seems you do not have to get every last drop of the old oil out. The system can tolerate some of the old stuff still in there but as long as you can still get -12 you would be best served trying to stay with it and not converting to -134.

[kings1527]

I'm not converting, I'm asking about using a modern r134a compressor in an R12 system.

[DMC3165]

I'm trying to determine what is most cost effective.

My compressor has a small leak near the hose on the back. It may also be the hose I'm not sure yet. The clutch is spitting out rust all over my engine bay so I'm going to assume it's slipping. I have r-12 in the system right now and most everything is original. Should I just replace the compressor and possibly the lines and have the system recharged with r-12. Or pony up the big bucks and have it converted to 134?

I will not be doing the work myself.

[David T]

I'm trying to determine what is most cost effective.

My compressor has a small leak near the hose on the back. It may also be the hose I'm not sure yet. The clutch is spitting out rust all over my engine bay so I'm going to assume it's slipping. I have r-12 in the system right now and most everything is original. Should I just replace the compressor and possibly the lines and have the system recharged with r-12. Or pony up the big bucks and have it converted to 134?

I will not be doing the work myself.

The clutch can be replaced but it may be cheaper to replace the compressor too. It may just be an "O" ring leaking but if you have the original hoses you should be replacing all 3 of them. I advise that as long as you can find someone who will still work with R-12 you should stay with it as long as you can.

[refugeefromcalif]

I advise that as long as you can find someone who will still work with R-12 you should stay with it as long as you can.

I still have an R-12 system in my car. I have a mechanic that will work on it but, I have to provide the freon.
Where's the best place to get R-12? Can it be bought somewhere Without getting a license?

George

[Henrik]

I'm trying to determine what is most cost effective.

My compressor has a small leak near the hose on the back. It may also be the hose I'm not sure yet. The clutch is spitting out rust all over my engine bay so I'm going to assume it's slipping. I have r-12 in the system right now and most everything is original. Should I just replace the compressor and possibly the lines and have the system recharged with r-12. Or pony up the big bucks and have it converted to 134?

I will not be doing the work myself.

Hi Chris,
The leaky system and a slipping clutch are unrelated. About the slipping clutch: Worst case, it may be because the compressor is about to seize. Let's hope not :) Much more likely is that the air gap of the clutch has worn over time and is too large => Not enough clamping force b/w rotor and armature. It is pretty easy to adjust it. Check out page 19, right here:
http://www.sanden.com/objects/Sanden%20SD%20Service%20Manual.pdf

Note that the clutch is "outside" the actual system. Removing it will not cause you to lose refrigerant. You should def look into this before you consider replacing the compressor.

[NightFlyer]

I still have an R-12 system in my car. I have a mechanic that will work on it but, I have to provide the freon.
Where's the best place to get R-12? Can it be bought somewhere Without getting a license?

George

Instead of using R-12, you may want to consider using an 12a product, which is essentially a hydrocarbon blended replacement. Redtek 12a, Freeze 12, Frostycool 12a, etc. Hydrocarbon based refrigerants actually operate at a lower head pressure, thereby extending the longevity of the compressor as it doesn't have to cycle as much, and get just as cold, if not colder than traditional R-12.

When the weather gets warmer here, I'll be flushing my A/C system and using an 12a refrigerant in the stock/OEM R-12 system.

Easier than trying to procure R-12, and IMHO, better.

[David T]

Instead of using R-12, you may want to consider using an 12a product, which is essentially a hydrocarbon blended replacement. Redtek 12a, Freeze 12, Frostycool 12a, etc. Hydrocarbon based refrigerants actually operate at a lower head pressure, thereby extending the longevity of the compressor as it doesn't have to cycle as much, and get just as cold, if not colder than traditional R-12.

When the weather gets warmer here, I'll be flushing my A/C system and using an 12a refrigerant in the stock/OEM R-12 system.

Easier than trying to procure R-12, and IMHO, better.

Although there are "replacements" for R-12 there is nothing that will work as well as R-12 in an R-12 system. You can buy R-12 on E-bay and at many wholesale supply stores that handle heating and cooling equipment "for the trade".

[kings1527]

I still have an R-12 system in my car. I have a mechanic that will work on it but, I have to provide the freon.
Where's the best place to get R-12? Can it be bought somewhere Without getting a license?

George

I've had outstanding luck on Craigslist, George. But just be sure to take your own scale with you to measure exactly how much R12 is still left in there. If you're looking at a 30 lb can, you have to figure about 10lbs for the can itself. Everything is so easy with the 30 lb in terms of filling your system and that should last you your entire life depending how much you get. Plus, you'll never have to worry about "should I convert or no". About 2.2 lbs of R12 in the DeLorean on a full charge.

If you get a 30 lb can that isn't sealed, just be sure the seller is somewhat reputable. In theory they could've filled it with something else or if it came from Mexico, there've been stories of propane being used instead of freon. I purchased one that had about 20 lbs left in it and never had a problem. And actually, propane is a pretty good refrigerant. It's just that whole "I sprung a leak on one of my AC hoses near my exhaust manifold and now I'm leaking propane onto my exhaust as I drive" that kind of makes it a bad idea in the eyes of the powers that be.

If you go with regular cans, just make sure they were stored in a dry and cool place. Light surface rust isn't a problem.

Most people within that market won't care if you have a license or not. At that, it'd take about 30 min to take a test and get it online. So I've been told.

[David T]

I've had outstanding luck on Craigslist, George. But just be sure to take your own scale with you to measure exactly how much R12 is still left in there. If you're looking at a 30 lb can, you have to figure about 10lbs for the can itself. Everything is so easy with the 30 lb in terms of filling your system and that should last you your entire life depending how much you get. Plus, you'll never have to worry about "should I convert or no". About 2.2 lbs of R12 in the DeLorean on a full charge.

If you get a 30 lb can that isn't sealed, just be sure the seller is somewhat reputable. In theory they could've filled it with something else or if it came from Mexico, there've been stories of propane being used instead of freon. I purchased one that had about 20 lbs left in it and never had a problem. And actually, propane is a pretty good refrigerant. It's just that whole "I sprung a leak on one of my AC hoses near my exhaust manifold and now I'm leaking propane onto my exhaust as I drive" that kind of makes it a bad idea in the eyes of the powers that be.

If you go with regular cans, just make sure they were stored in a dry and cool place. Light surface rust isn't a problem.

Most people within that market won't care if you have a license or not. At that, it'd take about 30 min to take a test and get it online. So I've been told.

Buying a large cylinder can be expensive. And if you don't weigh it you can't know what you are buying since it isn't sealed. Cans are the way to go for small quantities but you also must buy a can tapper and once you tap a can figure whatever you do not use will leak out. The most important thing is to make your system leak free. You should not have to add refrigerant for at least 5 years if you have a really tight system. If you got Propane you would smell it immediately and yes, it is dangerous to use (but it does work well!).

[Exolis]

Does anyone know how to order/what store part number to use for SD7H15QC4708 or even what other vehicle used that compressor to get it from a parts store like AutoZone or PepBoys?

[Henrik]

Does anyone know how to order/what store part number to use for SD7H15QC4708 or even what other vehicle used that compressor to get it from a parts store like AutoZone or PepBoys?

Look here: http://dmctalk.org/showthread.php?6692-A-C-Compressor&p=97275&viewfull=1#post97275

and here: http://dmctalk.org/showthread.php?6692-A-C-Compressor&p=97276&viewfull=1#post97276

[DMC5180]

A basic Google search of the full Part Number brought me to this sight.

http://www.discountacparts.com/sanden_compressor_SD7H15.htm

The 4708 Sanden number is listed with a full description of the build configuration.

Looks like they will build anything you want on demand. Probably worth giving them a call for a quote. Let us know what they say.

[Bopat]

Could somebiody help me with this problem?
I have a replacement gas for R12, but we don't know what pressure has to be.
The compressor is turning on and off quite often. What can be the problem? Too high or too low pressure?
Now the pressure is like it would be R12. But it's not....

Thanks

[DMC5180]

Could somebiody help me with this problem?
I have a replacement gas for R12, but we don't know what pressure has to be.
The compressor is turning on and off quite often. What can be the problem? Too high or too low pressure?
Now the pressure is like it would be R12. But it's not....

Thanks

What is the Replacement Gas?

Full charge using 134a is about 2.0 lbs or 0.9kg

[DMCMW Dave]

Could somebiody help me with this problem?
I have a replacement gas for R12, but we don't know what pressure has to be.
The compressor is turning on and off quite often. What can be the problem? Too high or too low pressure?
Now the pressure is like it would be R12. But it's not....

Thanks

Cycling too fast is low pressure (or cold outside temperature). At 70F the high pressure should hit about 200 PSI at cutout. There is a temperature table in the manual.

R134 will give higher pressures. HC refrigerants will be lower.

[David T]

Could somebiody help me with this problem?
I have a replacement gas for R12, but we don't know what pressure has to be.
The compressor is turning on and off quite often. What can be the problem? Too high or too low pressure?
Now the pressure is like it would be R12. But it's not....

Thanks

Not knowing what the replacement gas is and it's pressures, no one can tell you how much to put in and how to adjust the low pressure switch. If it is cycling too fast it could be you do not have enough refrigerant or the switch must be adjusted. Watch your high side pressures if you are going to try putting in more gas. If it gets too high you will shut down on the high pressure switch or pop the relief valve.

[Bopat]

The gas is 134a, as mentioned

[Henrik]

What is the Replacement Gas?

Full charge using 134a is about 2.0 lbs or 0.9kg

Technically, the correct R134a charge is 15% less (by weight) than the factory R-12 charge. From one application to another, the ideal charge may of course vary - only a so called Charge Determination test would reveal the correct charge, but again, as a rule of thumb: Factory R12 charge - 15% should be about the correct R134a charge.

During high load/high heat conditions an R134a system is much more sensitive to over-charging than R-12 is/was. If have seen the head pressure take off like a rocket and hit 450-500 psi in R134a wind tunnel testing when you would go, for example, from 60 mph to idle (i.e. no cooling whatsoever) @ 104 deg F. The same R-12 systems typically would never do that.

[Bopat]

The gas is 134a, as mentioned
Sorry - my mistake. The gas is 413A....

[Bitsyncmaster]

The 4xx type refrigerants are mixtures and therefor require you to charge liquid. If you charge with gas, you only get one of the refrigerants in the mixture.

[Henrik]

Sorry - my mistake. The gas is 413A....

WHOOA! All bet's are off. I know nothing about this stuff...

[Ron]

The 4xx type refrigerants are mixtures and therefor require you to charge liquid. If you charge with gas, you only get one of the refrigerants in the mixture.$.02
...and if you do this, you should charge it by using the low pressure switch port (bypass it with a jumper wire), otherwise you will lock up/destroy the compressor since liquid does not have enough time to expand to gas using the normal port right at the compressor (liquids will not compress).

[David T]

$.02
...and if you do this, you should charge it by using the low pressure switch port (bypass it with a jumper wire), otherwise you will lock up/destroy the compressor since liquid does not have enough time to expand to gas using the normal port right at the compressor (liquids will not compress).

I charge with liquid all the time. You have to be careful to do it slow enough or you do get liquid into the compressor and you will blow it up. I also have a device on the charging line that is supposed to break the flow into droplets to aid in charging. Filling with gas can take 10 times longer just because a gas has a much lower density than a liquid so to get the same weight of refrigerant in by gas takes a LOT longer. No matter what you do to fill the system you always start by jumpering the low pressure switch to force the compressor to run so you CAN fill it. Before starting the compressor I break the vacuum by putting in as much refrigerant as I can so I have some in there already before starting the compressor. BTW when charging the system good practice is to put a fan in front of the radiator even if you have electric fans in the car too. You know you got a working system when you see it "making water". First on the outside of the accumulator and then out the condensate hose.

[SS Spoiler]

Is it bad to hook up a refrigerant can so it remains vertical, open the valve and drive on. Iv'e recharged my truck on trips without wasting
road time.

[Henrik]

Is it bad to hook up a refrigerant can so it remains vertical, open the valve and drive on. Iv'e recharged my truck on trips without wasting
road time.

UUhhh.... not good. Once you turn your motor (or AC) off all pressures are going to equalize and your can may go ka-boom.

[Bitsyncmaster]

Charging with gas works fast with small cans if you put the can into a bucket of hot water when your charging the system. When you use a large 30 lbs tank to charge it does not get very cold. It's the liquid changing to gas that freezes the small cans.

[DMCMW Dave]

UUhhh.... not good. Once you turn your motor (or AC) off all pressures are going to equalize and your can may go ka-boom.

How will the low side ever get higher pressure than a sealed (new) can? Unless he's connected it to the high side, in which it will probably blow up before he gets the hood closed. . .

Not saying it's a good idea. . just asking.

[SS Spoiler]

Points well taken. The way I saw it the only difference in charging with a can the car was moving intend of stationary. Motor and AC
are both running either way. Still probably not a good idea as the can could shift into moving parts.

[Henrik]

How will the low side ever get higher pressure than a sealed (new) can? Unless he's connected it to the high side, in which it will probably blow up before he gets the hood closed. . .

Not saying it's a good idea. . just asking.

Good point, Dave. I was picturing the can stuffed away somewhere under the hood @say 200 deg F and since a large portion of the AC system is underhood too, the rest pressure would be fairly high i.e. subjecting the can to a pressure that it may not have been designed for.

[Exolis]

A basic Google search of the full Part Number brought me to this sight.

http://www.discountacparts.com/sanden_compressor_SD7H15.htm

The 4708 Sanden number is listed with a full description of the build configuration.

Looks like they will build anything you want on demand. Probably worth giving them a call for a quote. Let us know what they say.

So just an update on this, I emailed them asking for a quote with the part number and no response. Typically why I hate going to places like this, would prefer if there was something equivalent available at something like Pepboys, Autozone, etc.

[Henrik]

So just an update on this, I emailed them asking for a quote with the part number and no response. Typically why I hate going to places like this, would prefer if there was something equivalent available at something like Pepboys, Autozone, etc.

In post #41 I had posted:

Look here: http://dmctalk.org/showthread.php?66...ll=1#post97275
This is still valid. Read it.

and here: http://dmctalk.org/showthread.php?66...ll=1#post97276
I went back to Sanden's website but I can no longer find the option to buy from the site, BUT I found these distributors: http://www.sanden.com/Disttributors_NA.html. I bought my 4708 from A/C Warehouse. They are very helpful.

[Exolis]

In post #41 I had posted:

Look here: http://dmctalk.org/showthread.php?66...ll=1#post97275
This is still valid. Read it.

and here: http://dmctalk.org/showthread.php?66...ll=1#post97276
I went back to Sanden's website but I can no longer find the option to buy from the site, BUT I found these distributors: http://www.sanden.com/Disttributors_NA.html. I bought my 4708 from A/C Warehouse. They are very helpful.

Thanks, I sent them an email. Hopefully I'll get a response. Summit Racing seems to have some of the SD7H15s, but no idea if any are specifically the 4708.

[dustybarn]

I found it for sale on the Sanden website, but I'm not sure how I got there:

http://store.sanden.com/index.php/4708.html

[Exolis]

I found it for sale on the Sanden website, but I'm not sure how I got there:

http://store.sanden.com/index.php/4708.html

Thank you for the link. I tried using their part number search and I must of been putting in something wrong.

[Henrik]

Thank you for the link. I tried using their part number search and I must of been putting in something wrong.

Go to sanden.com.
Under Find Your Compressor and Model #, enter 4708
Click on Buy Now

[DMC5180]

Go to sanden.com.
Under Find Your Compressor and Model #, enter 4708
Click on Buy Now

Go to www.store.sanden.com

then search 4708

[kings1527]

So my temps have dropped off a bit which means that seal on my compressor is finally showing itself. I'm going to go ahead and order an SD7H15 in the 4708 configuration but make a special request through Sanden to have it sent without any PAG or Ester, if possible. I'll fill it with mineral oil so I can use it on my R12 system.

If there are any objections, please let me know!

[DMC3165]

Does anyone know if it's ok to remove a shim or 2 from behind the armature to tighten up the air gap a little? I rented a puller and picked up a feeler gauge today. Just by looking at it I can tell the air gap is too large. Since it has no other issues I'd like to try adjusting the air gap first.

[kings1527]

So....

I called Sanden today and the receptionist had no idea that they'd sell to private parties. I can go on their website right now and order one without any issues but I want to talk with a sales rep first to see if I can get one shipped to me without any PAG or Esther. She transferred me to sales and I left a message but didn't hear anything back. So I'm not sure how this is going to go.

Henrik, I know you used AC Warehouse. I'll look into them.

Does anyone know what model John Hervey is selling? I know it's a 134a compressor but not sure of the model. I'm guessing it's the exact one that I'm looking for (previous post). Worst case, I'll drain the factory oil the best I can and refill it with mineral oil for my R12 system.

Thanks!

[Ron]

Does anyone know if it's ok to remove a shim or 2 from behind the armature to tighten up the air gap a little? I rented a puller and picked up a feeler gauge today. Just by looking at it I can tell the air gap is too large. Since it has no other issues I'd like to try adjusting the air gap first.Yep, that's what they are for... :wrenchin:


Does anyone know what model John Hervey is selling?
Thanks!
SD508 ~1.5pg down here. (https://www.specialtauto.com/delorean-parts/AC-Cooling.html)

[DMC3165]

Yep, that's what they are for... :wrenchin:


Awesome. My air gap is a .043 slightly larger then the .016-.031 the manual recommends.

[kings1527]

Yep, that's what they are for... :wrenchin:


SD508 ~1.5pg down here. (https://www.specialtauto.com/delorean-parts/AC-Cooling.html)


I completely missed that, Ron. Thank you.

[kings1527]

The Delorean stock compressor is an SD-510Q8494 where :
- the 5 designates 5 cylinders
- the 10 stands for 10 cu in displacement per revolution
- Q is the type of cylinder head
- 8494 defines the combination of mounting, clutch size, offset, oil amount etc.
- this compressor used to be made at Sanden's old plant in Dallas, TX but is no longer in production (mostly because it was unable to withstand the higher pressures and loads/less efficient lubrication associated with R134a)

A perfect R134a drop-in replacement would be the Sanden SD7H15QC4708:
- the 7 designates 7 cylinders
- 15 stands for 155 cc displacement per revolution (about 9.5 cu in)
- this is a quieter, more durable compressor, specifically for R134a
- this compressor is produced in Wylie, TX
- I use this compressor on my D.

See attached drawings for both.

Henrik
former Application Engineer and Lab Manager at Sanden
1782917830

Hi Henrik,

Quick question. I know you say you use the 4708 in your car but after looking at the schematic for the unit, it shows the inlets for the AC hoses configured in a north/south fashion whereas our cars have the hoses in an east/west direction. Are there any issues with that? Did you simply rotate the unit?

Thanks!

[Henrik]

Hi Henrik,

Quick question. I know you say you use the 4708 in your car but after looking at the schematic for the unit, it shows the inlets for the AC hoses configured in a north/south fashion whereas our cars have the hoses in an east/west direction. Are there any issues with that? Did you simply rotate the unit?

Thanks!

That's correct, Alex. Just index the compressor 90 degrees.

[Henrik]

So....

I called Sanden today and the receptionist had no idea that they'd sell to private parties. I can go on their website right now and order one without any issues but I want to talk with a sales rep first to see if I can get one shipped to me without any PAG or Esther. She transferred me to sales and I left a message but didn't hear anything back. So I'm not sure how this is going to go.

Henrik, I know you used AC Warehouse. I'll look into them.

Does anyone know what model John Hervey is selling? I know it's a 134a compressor but not sure of the model. I'm guessing it's the exact one that I'm looking for (previous post). Worst case, I'll drain the factory oil the best I can and refill it with mineral oil for my R12 system.

Thanks!

LOL, that's quite amusing! If this would have been 10 years ago I could have told you that Sanden will not talk to anyone unless you are an OEM or a larger distributor. At best, they would have referred you to one of their distributors such as AC Warehouse (they're great by the way). So, I am really surprised that Sanden now offers the possibility to sell you a one-off compressor on their website, but hey, times are a-changing. Just for kicks, if you're up for it: I will PM you a couple a names to ask for if you want to give Sanden another try.

[Henrik]

Does anyone know what model John Hervey is selling? I know it's a 134a compressor but not sure of the model. I'm guessing it's the exact one that I'm looking for (previous post). Worst case, I'll drain the factory oil the best I can and refill it with mineral oil for my R12 system.

Thanks!

Alex,
The R134a compressor Hervey is selling is an SD5H14 http://www.specialtauto.com/delorean-parts/images/compressor-oil.jpg, which is the R134a equivalent (evolution, if you will) of the old SD-508 R-12 compressor. In other words, it is not an SD7H15 compressor. Either compressors are fine and durable. However, just fundamentally, the SD-5 was never intended for the automotive market (its primary use was/is heavy truck, tractors, agricultural, mining, off-road, military, marine etc etc). That is why I think the SD7H15 is the preferred choice because it is truly for the automotive market, primarily because it is quieter.

I am noting that the cylinder head fittings in Hervey's picture would not work on a Delorean.... but I guess that's why he is asking for your old cylinder head for the core so he can the swap cylinder heads.

[kings1527]

Got all the info, Henrik. Thanks again! Yeah, the receptionist there...when I started telling her what I was after, she said 'whoa whoa whoa...just...whoa. Are you private person? We only sell to big companies. Like Mitsubishi and companies like that. But let me transfer you to sales'.

I was like...'ok'. :confused: I told her that people have ordered single units from them before and she said that was news to her.

I knew you could order a one-off on the website but as more time goes on, the more I understand 'it's all about who you talk to'! I'll get in touch with them again tomorrow.

Thanks again, Henrik!

[kings1527]

Alex,
The R134a compressor Hervey is selling is an SD5H14 http://www.specialtauto.com/delorean-parts/images/compressor-oil.jpg, which is the R134a equivalent (evolution, if you will) of the old SD-508 R-12 compressor. In other words, it is not an SD7H15 compressor. Either compressors are fine and durable. However, just fundamentally, the SD-5 was never intended for the automotive market (its primary use was/is heavy truck, tractors, agricultural, mining, off-road, military, marine etc etc). That is why I think the SD7H15 is the preferred choice because it is truly for the automotive market, primarily because it is quieter.

I am noting that the cylinder head fittings in Hervey's picture would not work on a Delorean.... but I guess that's why he is asking for your old cylinder head for the core so he can the swap cylinder heads.

Again, huge info here, Henrik. I was wondering why he needed the old cylinder heads back. That definitely explains why.

So I guess you could even say that the original SD-510 was never really intended to be in our cars in the first place? That's interesting that they went with that. I'll DEFINITELY go with the SD7H15 and I'm glad I asked about all this. And glad we have such a great resource at our disposal here at the forum! Thanks Henrik!

[Henrik]

So I guess you could even say that the original SD-510 was never really intended to be in our cars in the first place? That's interesting that they went with that....

Well, let me correct myself somewhat by saying that the SD5 series was one of the very best and advanced compressors on the market 30+ years ago, even in cars..... Meanwhile, Sanden's main competition consisted of turn-off-the-century looking compressors, like the old cast iron, 2 cylinder CCI beast or the bulky, heavy Delphi A6 found in a lot of GM cars. But the automakers requirements have become so much more stringent since then. Air conditioning for one, used to be regarded as a nice-to-have add-on. These days everything is seamlessly integrated with the car and the expectation on AC performance, durability, noise, weight, size and cost is outrageous. This is of course driving better and better products, like the evolution of compressors. OK, enough from me about compressors.... (I do miss working in the industry though :))

[Ron]

$.02
Alex, if you order one from John, make sure you call him and verify (SD508/SD5H14) -- He is shows them both as R134a compressors and straightening out an order after the fact can be a nightmare.....
(It looks as if you get the SD508 unless you order a kit ??)

[kings1527]

I installed my new compressor (the 4708 model) and everything seems to be working just fine. Special thanks to Henrik's recommendations!

Some things that I learned:

-Sanden's customer service is horrendous. I had the issue with the receptionist who didn't know anything about private sales so she transferred me to sales and I left a message. Never heard anything back. I called a different day and left another message. Never heard anything back. At Henrik's recommendation, I tried to get in touch with a different person at Sanden but never got a call back from that person either. The only reason I had to get in touch with that person was to see if they could build/ship me a compressor with mineral oil instead since my system is R12. I eventually just ordered the unit off the website, drained the oil at home, and then refilled it with mineral oil. I think I got close to 4 oz out out of 4.5 oz that it was pre-filled with.

-The hose layout on the back of the 4708 is a little bit different than the SD-510 but all that's needed is indexing the unit by 90 degrees. Simple.

-I have Hervey's split line AC hoses and the connection on them is pretty fat. The M10 bolt that's supplied with the 4708 is too short to accommodate the hoses, plate, and washer. You'll have to use the original M10 (1.0 pitch) that's from your old unit. It's somewhat of a tough bolt to find in most cases.

-The 4708 is SUPER quiet and very smooth. Very nice design. I'll be running my AC a lot tomorrow to test everything out real well but all seems fine. No performance issues. So far while standing still, NORM AC with fan speed 2 and an ambient of about 65, I was getting about 38 degrees. I'm very interested to see what it is on a 100 degree day with good airflow over the condenser. Looks like we have some warmer weather making its way to SoCal in a couple days so I'll see what the deal is then.

-Hopefully I got enough of the original oil out of the unit so it won't cause problems down the road. I can't imagine such a small amount of PAG or the SP-something oil they put in it would cause issues with R12.

Again, the unit is very plug and play. Furthermore, I'd be careful with a NOS SD-510 compressor. Mine was sending oil out of the side and onto the cover where the three vacuum lines come out and I know mine wasn't the first to do that right out of the box. It took close to a year for me to say to myself "hmmmm.....my AC is cool but not cold anymore".

Here are some pics:

268192681826817

[kings1527]

Ok,

So I did some higher temperature testing with my system (about 95-100 degree ambient) and here's what I find:

-I'm at best getting about mid 50's cooling temp (maybe down to 52 or so if I drop the fan speed from 4 down to 2).
-If I'm around 80 ambient or so, I can get very low 40's, maybe 38-39. Very close to spec.

Here's what I know about my system:

-Perfectly charged to 2.2 lbs R12 the other day.
-No leaks
-No moisture in my system.
-If anything, I may have about 2 oz of extra mineral oil floating around. No more than that.

I need to do put the gauges on and double check my pressures but I started thinking about the changes in charge amounts between R12 and R134a. I know R134a is about 20% less if you're charging an original R12 system (compressor and all) with R134a. But now I'm dealing with the opposite. I'm wondering if my system needs 20% MORE R12 because the compressor was originally designed for R134a, and a slightly less displacement.

I know that the most common cause of cool but not cold AC is low refrigerant. I can't think of what else it would be and it's acting exactly like low charge when in a hot ambient. Low ambient is fine.

So my plan is to put in another 1/2 lb of R12 and go from there. But first I'll check my pressures.

Any other guesses or thoughts?

[hmcelraft]

When testing and taking the temp readings are you stationary with just the cooling fans working or, do you have a fan in front of the car to simulate driving? Or, are you driving around? 30 mph or more can create a lot of air flow thru the condenser. Is the inside air flow on "Max" (recirculate) or "Norm"(outside air)? You have the correct orifice tube installed? 2 oz or more of oil might cause lower efficiency at high temperature due to higher pressure but, if it is just 2 oz excess that should stay in the accumulator with no problem. Are you sure you have all of the air and moisture out of the system?

I have a Hervey compressor which is basically a 508 not a 510 - about 15-20% less capacity. At 95F outside, in traffic, I can start to run about 50F out of the vents and I have about 3oz of oil too much in my system. I just haven't messed with it because normally the temp is about 35-45F out of the vents - depending. I thought well, when it starts to be a problem I can get it right - that was 4 years ago - it is still the same. I mention this because it does sound like you have something going on. When I ran a 510 compressor and the system was set correctly it was about 40F out of the vents all the time. I might have to go to "Max" when it was 95- 100F. but it was cold out of the vents.

A 1/4 to 1/2lb of Freon isn't going to make any difference in the temp. It might change the cycle time in cooler weather. Also, the symptom you describe with the 510 type compressor at higher temperatures sounds more like an over-charge condition - not an under-charge. That's why the question about air flow across the condenser - same result - too high - high pressure side. 2.2 is the correct R-12 charge.

[kings1527]

When testing and taking the temp readings are you stationary with just the cooling fans working or, do you have a fan in front of the car to simulate driving? Or, are you driving around? 30 mph or more can create a lot of air flow thru the condenser. Is the inside air flow on "Max" (recirculate) or "Norm"(outside air)? You have the correct orifice tube installed? 2 oz or more of oil might cause lower efficiency at high temperature due to higher pressure but, if it is just 2 oz excess that should stay in the accumulator with no problem. Are you sure you have all of the air and moisture out of the system?

I have a Hervey compressor which is basically a 508 not a 510 - about 15-20% less capacity. At 95F outside, in traffic, I can start to run about 50F out of the vents and I have about 3oz of oil too much in my system. I just haven't messed with it because normally the temp is about 35-45F out of the vents - depending. I thought well, when it starts to be a problem I can get it right - that was 4 years ago - it is still the same. I mention this because it does sound like you have something going on. When I ran a 510 compressor and the system was set correctly it was about 40F out of the vents all the time. I might have to go to "Max" when it was 95- 100F. but it was cold out of the vents.

A 1/4 to 1/2lb of Freon isn't going to make any difference in the temp. It might change the cycle time in cooler weather. Also, the symptom you describe with the 510 type compressor at higher temperatures sounds more like an over-charge condition - not an under-charge. That's why the question about air flow across the condenser - same result - too high - high pressure side. 2.2 is the correct R-12 charge.

-My temps were taken during the ambients that I mentioned, and at times at highway speed. So I was definitely getting real good airflow. They were taken on MAX AC.
-Yes, I installed the correct orifice tube last year. It seems I'm getting way too much cooling as it is to be an OT problem. At lower ambients, around 75-80, I'm getting near spec cooling.
-I'll check my pressures and see if they're too high. That could clue me in as to too much oil in the system, which I'd be surprised.
-The difference in capacity between the 510 and the 4708 isn't much at all. I can't imagine this is the center of my problems.
-The only change to my system that I made was the new compressor and an additional maybe 2 oz of oil since I felt I may have lost that much during my leak. But those were the only changes.
-Checking my pressures will give me a good idea and I'll still put another 1/2 lb of R12 in the system and see if the temps and pressures change. Doing so won't hurt. But as a somewhat last resort if I can't figure anything else out, it'll be very telltale after I see if the temps change at all. That would be about an additional 20% of refrigerant, just about what they say you charge a r134a system LESS. I'm still wondering if that's factoring into my problem: can a r134a designed compressor require 20% MORE R12 in an R12 system as opposed to an R12 compressor requiring 20% LESS r134a in a r134a system? :confused:

Dunno. I'll do some tests and report back.

[David T]

-My temps were taken during the ambients that I mentioned, and at times at highway speed. So I was definitely getting real good airflow. They were taken on MAX AC.
-Yes, I installed the correct orifice tube last year. It seems I'm getting way too much cooling as it is to be an OT problem. At lower ambients, around 75-80, I'm getting near spec cooling.
-I'll check my pressures and see if they're too high. That could clue me in as to too much oil in the system, which I'd be surprised.
-The difference in capacity between the 510 and the 4708 isn't much at all. I can't imagine this is the center of my problems.
-The only change to my system that I made was the new compressor and an additional maybe 2 oz of oil since I felt I may have lost that much during my leak. But those were the only changes.
-Checking my pressures will give me a good idea and I'll still put another 1/2 lb of R12 in the system and see if the temps and pressures change. Doing so won't hurt. But as a somewhat last resort if I can't figure anything else out, it'll be very telltale after I see if the temps change at all. That would be about an additional 20% of refrigerant, just about what they say you charge a r134a system LESS. I'm still wondering if that's factoring into my problem: can a r134a designed compressor require 20% MORE R12 in an R12 system as opposed to an R12 compressor requiring 20% LESS r134a in a r134a system? :confused:

Dunno. I'll do some tests and report back.

1/4 to 1/2 lb of refrigerant is a lot. If you make any change it is in terms of ounces and probably no more than 1/4 lb total. You can try adjusting the low pressure switch and messing with the cycle times to increase cooling capacity. Too much refrigerant can REDUCE cooling capacity because it also raises low side temps (higher pressures = higher temps). Make sure both coils (condensor and evap) are clean. Can't hurt to clean them chemically to be sure they are clean and when testing you should have a fan in front of the car especially if it is hot. Too much oil can also reduce capacity but it would take a LOT more than a few extra ounces.

[Ron]

+1 on the 1/4 to 1/2 being a lot and time for gauges...Use the chart located in Resources (http://dmctalk.org/showthread.php?7921-AC-Pressure-Charts-Reading-Gauges-(R12-and-Retrofit)) (Note readings taken when clutch cycles out) at several ambient temps so you can tell what is going on...

[kings1527]

I took some pressure readings a little bit earlier with an ambient of about 89 degrees. My low pressure seemed to be doing fine, cutting out around 20 psi. My high side was about 250 psi at cutout. My center vent temp was about 50 degrees. I went back to my videos and my notes of last year when I was rebuilt my system and everything was working perfectly. Back then, my low side was cutting out about the same at 20 psi but my high side was about 190 psi at cutout.

So, I have a normal low side, but a high high side. My research is telling me that's due to an orifice tube obstruction/problem? It makes sense. The OT is obstructed and not letting enough freon flow through the evaporator and resulting in decreased cooling.

I did do a feel test on my evaporator inlet and outlet. Both felt to be about the same, if maybe the outlet was a tad cooler. I looked at N:09:02 in the manual (the flow chart) and that exact outcome was leading me away from an OT problem. But I know what my pressures are now and I know what they were a year ago when everything was perfect and I definitely have a high high side right now by about 60 psi.

Any other thoughts on this? I know for a fact my OT is going to be a pain to get out of there. I might try to torch it out and slightly melt/distort it. Thanks.

[Ron]

Actually you have Low-Low and High-High. It's out of both ranges (Targets @ ~90F are 28.5 & 185, for R12). If you are sure the charge was exact, suspect the orifice tube (restriction/adjustment) and a restriction in screen (receiver dryer).

A lot to search through...so to confirm:
System was blown out/flushed?
It had R12 with the previous compressor?
New Receiver-Dryer?
Engine is well within normal temp range when taking above readings?

[kings1527]

Actually you have Low-Low and High-High. It's out of both ranges (Targets @ ~90F are 28.5 & 185, for R12). If you are sure the charge was exact, suspect the orifice tube (restriction/adjustment) and a restriction in screen (receiver dryer).

A lot to search through...so to confirm:
System was blown out/flushed?
It had R12 with the previous compressor?
New Receiver-Dryer?
Engine is well within normal temp range when taking above readings?




Thanks Ron. I was going off of the tech manual which stated that the compressor should cut out between 20-28 psi but you're right, I'm low-low too.

I didn't flush my system when I installed my new compressor just the other day and yes, my system has always been R12. I completely rebuilt my system (new hoses, evaporator and orifice tube, accumulator, seals, and a NOS compressor just last year). When I installed my new orifice tube in the evaporator last year, it was a total pain to get in there and I'm wondering if something finally gave way after about a year. Maybe I damaged it along the way but it hung in there up until now. But everything happened all of a sudden. My system is totally brand new and for something to happen and cause a clog kind of puzzles me. The only thing I didn't replace last year was the condenser, which was flushed thoroughly at the time.

No, I did not install a new receiver-dryer. I had my system only open for about an hour while I installed the new compressor so I just drew a vacuum after the new compressor went in and I called it 'good'. My current receiver-dryer is only about a year old.

And yes, my engine was well within normal operating temps when all of the temps/gauge readings were taken.

[Ron]

Yeah, sounds like something restricting, but not blocking, the low side. Since the D's test ports are right at the compressor, it can be anything from the OT's screen> Evaporator> Receiver-Dryer (Accumilator)> Compressor Suction Port Screen, or the Lines connecting them (but they are new).

Odd balls:
Small amount of moisture in system (but it was vacuumed)
Switch (but was OK before)

...Air Box not draining all water (partial freez-up => restriction)
...Dirty condensor (external...but was OK before)
[Might take a flakey switch too with these two...don't have my OT v/s EV head in gear at the moment lol]

[kings1527]

I think my first order of business is going to try to get the OT out of the evaporator as cleanly as I can. The OT was driven in place with a makeshift tool so it's going to be a total bear to get out. Once that happens, I'll back flush the evaporator and I'll also put in a new accumulator too. While I'm in there, I'll flush the condenser again just to be sure but I can't imagine there'd be an issue there. It was perfectly fine before. I'll also flush the line that has the high pressure hub leading from the bottom of the condenser to the evaporator. I know we're focused on the low side but I'll replace/flush all those parts and might as well flush the high side while I'm at it, I guess.

If I can't get the OT out cleanly or at all, I'll put another evaporator in there. :facepalm: But that's fine. After doing it once and knowing what parts I need to have all lined up, I can get it done in a very long day or a couple days. One thing I learned with buying a new evaporator was make sure that the OT fits inside the inlet before you even take it home. Mine was so incredibly tight; more so than I ever think it should've been and I really had to make it work. I LOVED having my AC blow frigid cold. It's very mediocre now and I'm not liking it.

I can't imagine I'd have a blocked suction screen on my new compressor since it just came out of a box from the factory about 5 days ago. But who knows. I'm guessing that entails removing the back plate and the rest is pretty self explanatory?

And by way, my LP switch was brand new a year ago too. So I can't imagine a problem there.

Thanks again and please keep any more advice coming!

[Ron]

Sounds like you are on it to me :thumbup:.

RE: Suction screen restriction...
In your case (new compressor), trash could have came from anything upstream, up to the OT screen -- No telling what might turn loose when you disturbed it all...

[David T]

Yeah, sounds like something restricting, but not blocking, the low side. Since the D's test ports are right at the compressor, it can be anything from the OT's screen> Evaporator> Receiver-Dryer (Accumilator)> Compressor Suction Port Screen, or the Lines connecting them (but they are new).

Odd balls:
Small amount of moisture in system (but it was vacuumed)
Switch (but was OK before)

...Air Box not draining all water (partial freez-up => restriction)
...Dirty condensor (external...but was OK before)
[Might take a flakey switch too with these two...don't have my OT v/s EV head in gear at the moment lol]

It takes a lot for the orifice tube to get plugged up. There is a large screen that will catch most anything that could plug the tube up. Most likely explanation is the condenser coil is not transferring enough heat causing the high side to go high and lowering the low side. That can happen because your ambient temp is higher than last time, the airflow is lower, or the coil is dirty. The humidity also has a large effect. If you are not cycling enough, at pressures below 32 psi, the evap coil can freeze up blocking airflow raising high side pressures. I would not go after the orifice tube just yet.

[Ron]

It takes a lot for the orifice tube to get plugged up.
Agreed, but we're thinking something may be partially plugged, just restriction, if anything...

[kings1527]

It takes a lot for the orifice tube to get plugged up. There is a large screen that will catch most anything that could plug the tube up. Most likely explanation is the condenser coil is not transferring enough heat causing the high side to go high and lowering the low side. That can happen because your ambient temp is higher than last time, the airflow is lower, or the coil is dirty. The humidity also has a large effect. If you are not cycling enough, at pressures below 32 psi, the evap coil can freeze up blocking airflow raising high side pressures. I would not go after the orifice tube just yet.

Thanks David. I'll check my condenser but I'm confident everything is ok with it. I'll check to make sure the coil is clear of debris and I'll flush it first when I open the system and see if there's anything obvious during the flush. Out of curiosity, is it easy for the condenser to become blocked with debris or is it large enough for things to pass through? But I'll check externally to make sure everything looks good as far as heat transfer goes.

I'm wondering if something is partially obstructing that first large screen on the orifice tube, restricting refrigerant flow to a certain degree.

On another note with the orifice tube problem. Will my evaporator inlet/outlet tubes be different temperatures or the same temp if I have a blockage or an orifice tube problem? The reason I ask is that they are the same temp after the orifice tube on the evaporator side. Very roughly. Definitely not a big difference between the two, if at all.

[Ron]

The exterior of the condenser doesn't have to be clogged to loose efficiency, several things can coat it and reduce heat transfer.
The temp of the evaporator's output tube should be warmer, it's job is to transfer heat from the air inside the box to the refrigerant inside the evaporator, then it's onto the the condenser, which does the opposite), see?

[David T]

The exterior of the condenser doesn't have to be clogged to loose efficiency, several things can coat it and reduce heat transfer.
The temp of the evaporator's output tube should be warmer, it's job is to transfer heat from the air inside the box to the refrigerant inside the evaporator, then it's onto the the condenser, which does the opposite), see?

You should see a large delta T before and after the orifice tube and another large delta T between the inlet and outlet of the evap coil. When I mentioned blockage on the condenser coil I meant on the air side. Unless the insides of your system are coated in the "black death" because of heavy contamination, there should be no problem inside. If you do not see a large delta T between the inlet and outlet of the evap coil you are either starving the coil (blocked orifice tube or low refrigerant) or there is not enough airflow. Does the A/C make water? At 20 degrees (20 psi) you may be freezing up the evap coil. If you are not cycling enough at that pressure you WILL freeze it up, especially in high humidity. The cycling is kind of like a defrost mode allowing the coil to warm up enough to shed any ice. The Delorean doesn't have any of the fancy (read complicated) valving to prevent coil freeze-up. That's why it MUST cycle. The typical symptom is plenty of cooling initially but the longer it runs the less it cools and it stops "making water" (it's now making ice!). Eventually the compressor will stop on the high pressure switch or you will pop the relief valve. Or you may see the compressor belt slipping or you can blow hoses.

[kings1527]

Thanks guys. Here's a video I did of my issue. This was done with an ambient of about 85. My high side gets up to about 250 with a slightly higher ambient. My vent temp will get to about 45 at the lowest with these ambients and up to about 60 depending on the cycle. I'm also not seeing any icing of the exterior of the accumulator at these pressures, so I don't think my evaporator is icing up. Also, my airflow through the vents has been great. Another reason why I don't think my evaporator is turning into a block of ice.

Taken just now:
https://www.youtube.com/watch?v=33--LEeNn6U&feature=youtu.be

Here's another video I did last year dealing with adjusting the LP switch but you can see how different my high side was back then. Much more normal numbers:
https://www.youtube.com/watch?v=76ujceVWebE

I cleared out my evaporator drain so I know there's no blockage. Plus, I use MAX a lot more frequently and I believe that cuts down on condensation compared to NORM.

[Ron]

You still have the cut out too low. It should be 25-32 psi, I'd go for the higher end for now...
FWIW- If you had not of said "engine temp norm", "evacuated" and "exactly 2.2 lbs", I'd suggest fixing the cut out point and bleeding off a little refrigerant...

[kings1527]

You still have the cut out too low. It should be 25-32 psi, I'd go for the higher end for now...
FWIW- If you had not of said "engine temp norm", "evacuated" and "exactly 2.2 lbs", I'd suggest fixing the cut out point and bleeding off a little refrigerant...

Thanks Ron. I forgot to mention that yes, my engine temp was normal, everything had been evacuated and I'm sure I filled it with 2.2 lbs. I used a digital scale when I filled it last.

I'll try adjusting the LP switch and see where that gets me. But after looking back at my other video, when I was about 38 psi on the low side, I was at about 85 psi high side when all was working fine. Now at about 40 psi low side, I'm now at 140 psi high side. Definitely sounds like a restriction from what I can see. Which makes sense - if I have that restriction and freon isn't able to get to the evaporator because of that restriction, my temps will be REAL warm (65+) at the top end of the cycle which is exactly what's going on.

[Ron]

Yeah, sounds like it. ...but I'd try the switch then double check everything, yeah, one more time :deviltail:

I wish someone had a list of temps at all of the key points from a proved D system. It would help with a lot of troubleshooting ..and give a good excuse for a toy..um..infrared thermometer :smile:.

[kings1527]

Sounds great, thanks Ron.

And my last question for 10 minutes: if I want to check the suction screen on the compressor to make sure there isn't any debris clogging that screen, all I have to do is take off the compressor back and is the screen readily accessible? Self-explanatory to get to it once I get the compressor back removed?

Thanks again.

[Ron]

lol
I'm not sure on that model. ...IIRC, you should be able to tell by removing the hose(s).

[kings1527]

Excellent, thanks again. I won't be able to break everything down until Wednesday so I'll know more then.

I can't imagine that a serviceable part such as the suction screen would be difficult to get to but I've been wrong more times than I've been right! I think the overall design of my new compressor is very much like the SD-510.

[Ron]

...and don't be surprised if it doesn't have one.

Good Luck!

[Henrik]

: ...can a r134a designed compressor require 20% MORE R12 in an R12 system as opposed to an R12 compressor requiring 20% LESS r134a in a r134a system? :confused:

Dunno. I'll do some tests and report back.

Absolutely not. The compressor is not designed with the thermodynamic properties of a specific refrigerant in mind. "Designed for R134a" means that it is beefed to handle higher pressures and the poorer "miscibility" of PAG and R134a (PAG and R134a does not mix as nicely as mineral oil and R12 does/did - the result is a poorer oil circulating ratio, meaning that the PAG oil wants to get stuck wherever it can in the system, especially on the vapor/cold side of the system).

Also, actual capacity of the SD7H15 and SD-510 are very close all things being equal such as clutch diameter etc. Compressor capacity of a Delorean is plenty regardless of if you choose a 508 (5H14), 7H15 or a 510. Given that the cabin volume is so small the evaporator heat load is relatively small. We all know how the AC on pickup trucks spits ice cubes...

The cut-out setting of the low side low pressure cut-out switch should be as low as possible but when you take the pressure drop between the evaporator and the switch into account, the equivalent saturation pressure in the evaporator (at the time the switch cuts out) should be at a pressure that's equivalent to a saturation temperature that is j-u-s-t above 32 deg F. Let me know if you need help figuring this out.

An unclogged drain tube is good but the evap can STILL be full of capacity killing (and smelly) mildew and cob webs... there are sprays for that.

What's this stuff about a suction screen on the compressor??? Never seen one but if there is one - get rid of it! Restricting the compressor on the low side can cripple it big time. If anything, the orifice tube is your filter. BTW, when you check the orifice tube, make sure it is seated properly too (no leakage).

[Henrik]

... and another large delta T between the inlet and outlet of the evap coil. .... If you do not see a large delta T between the inlet and outlet of the evap coil you are either starving the coil (blocked orifice tube or low refrigerant) or there is not enough airflow..

WRONG, David. In an AC system using an orifice tube instead of a TXV the refrigerant going through the evaporator is at 100% saturation throughout the evaporator. There is 0 superheat. This means that the refrigerant will not change in temperature between the inlet and outlet (even though it has absorbed a bunch of heat as it makes its way through the evap). If the outlet is warmer than the inlet then you are undercharged. So how do you make sure the refrigerant always is in a vapor state by the time it arrives at the compressor you may ask?: That's the sole purpose of the accumulator.

[SS Spoiler]

" Sir Henrik " has spoken.

[Ron]

What's this stuff about a suction screen on the compressor??? Never seen one but if there is one - get rid of it! Restricting the compressor on the low side can cripple it big time. If anything, the orifice tube is your filter. Never seen one?? You must be a Ford man :deviltail:

One of two kits to keep up with GM's stuff. ( Don't try and defect one with it missing... ;-)
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[Henrik]

Well, sh*t. My wife is having an all-ladies party and I am stuck in the back of the house so I just wrote up a long dissertation about taking pressure drops into account when determining the ideal pressure setting and then I accidentally erased the whole thing.:rant:

I am wondering if there is a "draft" copy stuck somewhere. Oh well...

[Henrik]

Never seen one?? You must be a Ford man :deviltail:

One of two kits to keep up with GM's stuff. ( Don't try and defect one with it missing... ;-)
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Well, I'll be darned....

[Henrik]

Well, sh*t. My wife is having an all-ladies party and I am stuck in the back of the house so I just wrote up a long dissertation about taking pressure drops into account when determining the ideal pressure setting and then I accidentally erased the whole thing.:rant:

I am wondering if there is a "draft" copy stuck somewhere. Oh well...

Well it went something like this:

If you want the coldest possible air temp out of your vents the air going across the evap should be as close to possible as 32 deg F as possible; not lower or ice will be forming on it. Let's go with 34 deg F to be safe. This equates to a 31.7 psi saturation pressure in the evap (attached chart). Then, assume a 2 psi pressure drop from the evap to the switch = 29.7 psi. Then, assume your gauges are hooked up at the compressor, so let's assume a 6 psi pressure drop. This mean that your gauges should read 24 psi when the switch cuts out.

The above assumes idle condition. At 2,000 rpm the pressure drop is greater, let's assume a total of 12 psi, so ideally your gauges should read 20 psi when the switch turns off the comp at that speed.

The perfect place to measure the pressure is obviously at the evaporator but the OEMs rarely provide a pressure tap there. But, hey, you can always measure the pressure at the switch location (using a "tee")!
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[kings1527]

Henrik,

You're blowing my mind. Thanks for all the info. Nice to know that I'm probably not going to find a screen on the suction side of my compressor. I have no idea what the cause of my obstruction is on the low side but I'm guessing maybe my dessicant bag in the accumulator took a dump and sent stuff through my system. I have no idea what else it can be since my whole system was brand new a year ago. It worked perfectly for nearly a year after I did everything.

My only concern is making sure there isn't any remaining dessicant in my new compressor that will A) damage the compressor, or B) send those particles through my system after I clean and flush everything out and put me right back to where I started.

[Ron]

Nice to know that I'm probably not going to find a screen on the suction side of my compressor. I have no idea what the cause of my obstruction is on the low side but I'm guessing maybe my dessicant bag in the accumulator took a dump and sent stuff through my system.That is exactly what a screen is there to prevent??? ie protect the compressor...everything else is virtually steel or aluminum pluming that never causes trash problems.

[kings1527]

That is exactly what a screen is there to prevent??? ie protect the compressor...everything else is virtually steel or aluminum pluming that never causes trash problems.

And that makes total sense. I hope mine does just in case my accumulator gave out. But I'm hearing that some Sandens might not have one and it seems like it'd be a great idea to have one if it doesn't compromise functionality. It seems like some have one and some don't.

[Henrik]

The Sanden compressor itself does not come with a suction screen from the factory so that must be an add-on. BTW, the accumulator has its own screen and so does the orifice tube so I think you're covered from a filtering perspective :)

Any particular indication that leads you to believe you have loose desiccant in the system?

[kings1527]

The Sanden compressor itself does not come with a suction screen from the factory so that must be an add-on. BTW, the accumulator has its own screen and so does the orifice tube so I think you're covered from a filtering perspective :)

Any particular indication that leads you to believe you have loose desiccant in the system?

Great to know from a filtering perspective!

I don't really know what else could be causing a blockage at my orifice tube or somewhere else on the low side (accumulator perhaps) because I completely rebuilt my system last year. Brand new everything with the exception of the condenser which was flushed thoroughly. So I don't know where else an obstruction could've come from or how it would've developed.

I guess if it were desiccant, it would've had to pass through the compressor and at no point did I have any noise or performance problems. I've come across info that says if there were moisture in the system, that could cause corrosion and develop particulate. But I can't see how else any of this would've developed.

I won't be able to open up my system until Wednesday and I'm looking forward to cutting open my accumulator and examining my orifice tube, which I'm probably going to have to cut out of my evaporator. My OT is locked in place past that first hub that you slide it past in the evaporator inlet. I'll try to get it out but it looks like everything is going to have to come out.

[David T]

Great to know from a filtering perspective!

I don't really know what else could be causing a blockage at my orifice tube or somewhere else on the low side (accumulator perhaps) because I completely rebuilt my system last year. Brand new everything with the exception of the condenser which was flushed thoroughly. So I don't know where else an obstruction could've come from or how it would've developed.

I guess if it were desiccant, it would've had to pass through the compressor and at no point did I have any noise or performance problems. I've come across info that says if there were moisture in the system, that could cause corrosion and develop particulate. But I can't see how else any of this would've developed.

I won't be able to open up my system until Wednesday and I'm looking forward to cutting open my accumulator and examining my orifice tube, which I'm probably going to have to cut out of my evaporator. My OT is locked in place past that first hub that you slide it past in the evaporator inlet. I'll try to get it out but it looks like everything is going to have to come out.

To get dessicant into the compressor it would have to go through the orifice tube. I don't see that happening. If there is a screen on the compressor it is only to keep out the large junk. By the time you get the orifice tube out it is difficult to tell if it is plugged up if you have to damage it to remove it. If the dryer was shedding dessicant you will find it covering the screen for the orifice tube. More likely the tube and screen was getting plugged up by moisture freezing on it, not dessicant. How hard and how long did you evacuate the system?

[Henrik]

To get dessicant into the compressor it would have to go through the orifice tube. Well, no... because the OT is upstream of the accumulator.


By the time you get the orifice tube out it is difficult to tell if it is plugged up if you have to damage it to remove it. If the OT screen is clogged it will be very obvious when you pull it out, regardless if you damage it. Just look at my OT (attached) from when I overhauled my AC in 2006. Now, keep in mind that even though the OT screen is dirty, you may still be OK to a certain extent. What matters is the actual orifice tube inside of it (it looks like little pipe) which is what creates the pressure drop from high to low pressure.
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More likely the tube and screen was getting plugged up by moisture freezing on it, not dessicant. How hard and how long did you evacuate the system? That's an interesting angle but I think Alex said he vacuumed the system pretty well and if the OT froze up completely the suction pressure would go into a vacuum.

[Henrik]

Hey Alex, I am too lazy to go through the thread to recall what the actual symptom is but I think it was basically that you're not getting cold air out of the vents at higher outdoor temps.

Have you checked to make sure the air ducts haven't come loose??? When I re-did my interior last year I had a HELL of a time sliding the air ducts (pn 101697) onto the back of the air vents. It's like they wanted to slip back off on their own. Before you rip the whole system apart I would crawl under the dash and check the integrity of all of the air ducting.

In my mind, AC problems are usually less complex than you might think.

[kings1527]

Thanks guys. Yes, I vacuumed it out for about an hour every time I've opened the system. Maybe some moisture stayed in and created mildew that caused the block? I have no idea. But I would imagine that my compressor would've taken a beating if desiccant were drawn through it.

Not a problem, Henrik. This thread is getting really long. Basically, my issue is this:

-completely rebuilt system (minus the condenser) a year ago. Flushed the condenser thoroughly.
-installed a NOS SD-510 last year but it turned out it had a small clutch seal leak
-vacuumed out and held for about an hour. No leaks.
-filled with R12 via digital scale, 2.2 lbs
-system worked perfectly within spec for nearly a year
-had a sudden onset change in outlet temp from 'cold' to 'cool' about a month ago. I thought maybe the problem was the compressor which leaked out enough R12 and caused a drop in performance.
-installed the new 7 series Sanden
-same results with cooling as with the 510
-pressure tested my system and I'm having a high-high side and a low-low side. My high side is around 60psi higher than were it should be given the ambient (250 psi when it should be 190). All indication is pointing to a low side restriction but I'm going to go through and flush everything out when I break it down.
-my orifice tube is really in there so I'm probably going to have to do an evaporator again. I mean, it's REALLY in there. I'm convinced my evaporator that I put in a year ago had a slightly smaller diameter inlet than what it should've been, maybe by 1/32 or so.
-I have NO idea why I'd have a restriction. It was virtually a brand new everything but I'm sure I didn't do something right somewhere.

I'll check the ducting but I'm pretty confident that things are ok with it. With an ambient of close to 90, I get temps ranging from 49 to about 65 along with a low side PSI of about 20 right before cutout and a high of about 250 psi. Here are my latest gauge readings with a slightly cooler ambient and not as high of a high side. But it's still too high:

https://www.youtube.com/watch?v=33--LEeNn6U

[Ron]

An after thought- Have you tried your old/different cycle switch?

[kings1527]

An after thought- Have you tried your old/different cycle switch?

I haven't tested that or thought of that. I'll give it a shot.

[David T]

I haven't tested that or thought of that. I'll give it a shot.

To get book readings the car and all of it's systems has to be exactly right. For instance, if the ducting in the doors is very leaky you can loose a LOT of cold air inside the doors and that will reduce capacity and affect the pressure readings. The idea is to get close to them, not exactly them. Humidity, ambient temperature, air pressure, sunlight, all will have an effect. There is also instrument error. Did you check your gauges to zero them before hooking them up and how accurate are they? How many times have they been dropped? As important as how long you evacuated the system is how hard a vacuum did you pull? You have to boil out as much of the water vapor as you possibly can and you do that with a hard vacuum for at least 1/2 hour. You cannot read a hard vacuum on a compound gauge. You need an electronic gauge to read microns or Torr.

[Henrik]

...filled with R12 via digital scale, 2.2 lbs...

Not to beat this topic do death, Alex (yes it is hard to troubleshoot from afar): I was wondering about what scale you would use to measure the 2.2 lbs: If you charged the system with the little 12 oz cans: Did you use/even need a weight scale? Or, if you had a larger, say 30 lbs R-12 tank - what scale did you use? Personally, I have a 30 lbs R134a tank and using a bathroom scale that has sufficient range but still the 0.1 lb accuracy I have found it to be e-x-t-r-e-m-e-l-y flaky.

Back at Sanden we used lab grade scales that had both the range and a repeatable accuracy down to 0.05 lbs but you probably don't have that.

My point: How confident are you that you put the right charge in there?

[kings1527]

Not to beat this topic do death, Alex (yes it is hard to troubleshoot from afar): I was wondering about what scale you would use to measure the 2.2 lbs: If you charged the system with the little 12 oz cans: Did you use/even need a weight scale? Or, if you had a larger, say 30 lbs R-12 tank - what scale did you use? Personally, I have a 30 lbs R134a tank and using a bathroom scale that has sufficient range but still the 0.1 lb accuracy I have found it to be e-x-t-r-e-m-e-l-y flaky.

Back at Sanden we used lab grade scales that had both the range and a repeatable accuracy down to 0.05 lbs but you probably don't have that.

My point: How confident are you that you put the right charge in there?

I'm confident the right amount of charge went it. I fill off of a 30 lb R12 tank and I use a postage digital scale that reads to the tenth of an ounce. When I filled my system last year and everything went well, I had used the same scale. I can't imagine the wrong amount of charge going in.

[kings1527]

So I opened up the system and the first place I checked was the high pressure line off of the hub leading straight to the orifice tube. As expected, there was no way to get the tube out but I COULD get the tube out enough to see about 4/5 of the large screen. I was hoping to see something that would indicate a blockage but didn't seen anything. And just by seeing that much screen, it looked like it would have plenty of room to not cause a block.

So now I'm looking at something in the accumulator or somewhere downstream. My plan is to leave the evaporator in place, flush out everything (minus the evaporator since the OT is still in there) and go from there. Now I'm suspecting something in the accumulator which would be a total break.

Any other ideas?

How common is it for an accumulator to 'fail'?

Thanks!

[Bitsyncmaster]

Are you using a standard orifice? The VOV type can not be bent in the tube.

[Ron]

Did you happen to check the pressures after bleeding some off?

[kings1527]

Dave: just a standard orifice tube and everything looked nice and straight.

Ron: I bled off some of it and nothing changed with it. I had the same results.

I'm at work tomorrow so I'm going to take my old accumulator with me and do an autopsy on it. I don't know if it means anything, but I shook my old accumulator after I took it out and I could hear the desiccant inside it shaking around. I shook my new accumulator and it didn't make any noise. Hmmmm. I installed the new accumulator, flushed the condenser, and put new O-rings on.

I've closed up my system and I've vacuumed the system over the past 2+ hours. I'm now holding a vacuum on it as I type this to make sure there aren't any obvious leaks but I'll charge it tonight and take a look at the pressures and the temps. I'll report back in a bit. Thanks again for all of your help. I really appreciate it.

[David T]

Dave: just a standard orifice tube and everything looked nice and straight.

Ron: I bled off some of it and nothing changed with it. I had the same results.

I'm at work tomorrow so I'm going to take my old accumulator with me and do an autopsy on it. I don't know if it means anything, but I shook my old accumulator after I took it out and I could hear the desiccant inside it shaking around. I shook my new accumulator and it didn't make any noise. Hmmmm. I installed the new accumulator, flushed the condenser, and put new O-rings on.

I've closed up my system and I've vacuumed the system over the past 2+ hours. I'm now holding a vacuum on it as I type this to make sure there aren't any obvious leaks but I'll charge it tonight and take a look at the pressures and the temps. I'll report back in a bit. Thanks again for all of your help. I really appreciate it.

Unless you have the "Black Death" I do not know of any accumulator/dryers failing besides becoming over-saturated with moisture or debris.

[Henrik]

And just by seeing that much screen, it looked like it would have plenty of room to not cause a block.
Remember, it is not the screen that would cause a blockage but the teeny tiny pipe inside the OT. You can't inspect the OT for possible blockage unless you remove it (and IIRC, it's even hard to see a blockage with it removed since the screen is in the way.)


My plan is to leave the evaporator in place, flush out everything (minus the evaporator since the OT is still in there) and go from there. Now I'm suspecting something in the accumulator which would be a total break.
If anything, the evaporator would be one of the more important components to flush out. In here, the refrigerant is in a low density, slow-moving, cold vapor state going through lots of bends, i.e. if you suspect crud in the system, this is where it would collect. However, flushing the evap by pushing liquid through the OT may not be very effective as the OT is hugely restrictive.


How common is it for an accumulator to 'fail'?
See attached picture. As mentioned before, the purpose of the accumulator is to ensure that the refrigerant is always in a vapor state before it goes to the compressor. That is why the "J tube" is open at the top so vapor-only can enter there. (This also gives you a visual of what would happen if the system was over-charged => liquid refrig would go to the compressor - not good.) Now, there is a tiny hole at the bottom of the J tube which purpose is to siphon out the oil from the bottom and blend with the vapor refrigerant before it goes to the compressor. Now, this oil hole has (should have) a very fine mesh filter covering it. So, my point is, even though the desiccant bag busted wide open, there is really no way for it to leave the accumulator and go anywhere else. I don't think the desiccant pellets would fit into the little oil hole in the unlikely even if the screen was missing.
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[David T]

Remember, it is not the screen that would cause a blockage but the teeny tiny pipe inside the OT. You can't inspect the OT for possible blockage unless you remove it (and IIRC, it's even hard to see a blockage with it removed since the screen is in the way.)


If anything, the evaporator would be one of the more important components to flush out. In here, the refrigerant is in a low density, slow-moving, cold vapor state going through lots of bends, i.e. if you suspect crud in the system, this is where it would collect. However, flushing the evap by pushing liquid through the OT may not be very effective as the OT is hugely restrictive.


See attached picture. As mentioned before, the purpose of the accumulator is to ensure that the refrigerant is always in a vapor state before it goes to the compressor. That is why the "J tube" is open at the top so vapor-only can enter there. (This also gives you a visual of what would happen if the system was over-charged => liquid refrig would go to the compressor - not good.) Now, there is a tiny hole at the bottom of the J tube which purpose is to siphon out the oil from the bottom and blend with the vapor refrigerant before it goes to the compressor. Now, this oil hole has (should have) a very fine mesh filter covering it. So, my point is, even though the desiccant bag busted wide open, there is really no way for it to leave the accumulator and go anywhere else. I don't think the desiccant pellets would fit into the little oil hole in the unlikely even if the screen was missing.
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The accumulator/dryer does a few different things. It is a container for the dessicant to absorb moisture from the refrigerant. It captures the refrigerant as it comes out of the evaporator and separates it into the vapor and the liquid. It holds excess oil and refrigerant. It is a place for the refrigerant to "accumulate" in different amounts as necessary depending on ambient temperature. It prevents liquid from getting to the compressor. It removes pulses to allow a smooth flow of vapor to the suction side of the compressor. The A/C system in a Delorean is somewhat unusual because of the lack of control valves, no expansion valve (a fixed orifice tube), and the very long lines to the compressor. For what it is, it is surprising how well it works without freezing up. Only in an automotive application do you see a system with a pump that changes capacity. Typically an electric motor runs the pump at a constant speed like a refrigerator. To give you some idea of what you are doing a rough rule-of-thumb is 1 lb of refrigerant can cool 12,000 BTU. With 2.2 lbs you are running an A/C with about 26,000 BTU capacity, about 2 tons. Enough for a small house! If you let the suction pressure get too low for too long it doesn't take long to freeze the evap coil solid! To properly operate the system you can't run the evap coil below 32 degrees F. Usually you won't run the coil below 34 just to give you a little margin. On the Delorean it is much lower that that so how do you keep the coil from freezing? Because it is so low the evap coil gets starved because the orifice tube can only allow so much refrigerant to pass so the low pressure switch shuts the compressor down till the evap coil gets flooded again with more liquid to raise the pressure. During that time the hot air passing over the evap coil acts like a defrost mode and melts any ice. A very fine line which is why if you do not use the correct fill of refrigerant you cannot get the system to operate properly. It is all sized to work so if you change the compressor to a different model or install a VOV or mess with the adjustment of the low pressure switch or try to use -134, you have to know what you are doing.

[kings1527]

So I cut apart the accumulator just to see if there was anything interesting inside that would give away my problem but didn't see anything. Anyways, I'll have a new accumulator in along with a new condenser within about a week....my work and parts arriving, willing.

If you've ever wondered what's inside your accumulator, here you go. It's interesting seeing exactly how the accumulator does its thing. You can see how it receives refrigerant from the port that's attached to the evaporator. From there, it finds itself within the entire accumulator until it's drawn out on the suction side back towards the compressor. You can also see how the schrader valve opens up into basically nothing: it just sits there within the accumulator.

The desiccant bags (green and there's two of them) just rest there near the bottom and for those to be torn open and send desiccant throughout...that would take quite an act. Those things look very sturdy but I did cut one as I was getting the accumulator open.

It also looks like there's a small inline filter at the bottom of the tube inside the unit.

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[Ron]

Remember, it is not the screen that would cause a blockage but the teeny tiny pipe inside the OT. You can't inspect the OT for possible blockage unless you remove it (and IIRC, it's even hard to see a blockage with it removed since the screen is in the way.)FWIW- I see "black death" and sometimes other misc things totally block the screen off quite often. Both ends of the tube are protected by a screen -- If there is anything (other than ice) blocking the tube itself, the screen has been damaged.

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Note: Always replace the accumulator after flushing. Some argue about whether the desiccant gets contaminated in the process or not, etc...., regardless, this process, or any other reason allowing it to be exposed to air for 5 minutes (total), saturates it, requiring accumulator replacement anyway.