A/C Compressors

[WHO1DMC]

A/C bearings went out, squeal smoke and :sad30: looking at the sd7 or sd508 compressors. Looking for the least drage on the engine. Any thoughts or piont outs to other posts?

Thanks Dave

[Henrik]

A/C bearings went out, squeal smoke and :sad30: looking at the sd7 or sd508 compressors. Looking for the least drage on the engine. Any thoughts or piont outs to other posts?

Thanks Dave

Huh? Try to re-word your question and I'm sure I can help.

[WHO1DMC]

Looking for a A/C compressor. Any help?:confused0:

[content22207_2]

eBay is full of them. To use an OEM back plate you need a 5 cylinder compressor (5 hold down bolts), not a 7 cylinder (7 hold down bolts bolts). A compressor with a V belt pulley already installed will basically be plug & play -- just swap the back over and fill it with oil -- but if you find a really good deal on a compressor with a serpentine pulley it might be worth buying it and swapping the pulley as well. Made in China compressors typically have the part number only, if any, cast or stamped into the body. Honest to goodness Sanden compressors have a stick on label with much more information, unless the Chinese are knocking those off now as well. Made in China compressors are about a hundred dollars. Sanden compressors are $150-$200, but if you're patient those pop up closer to $100 as well, sometimes even less (my second compressor was only $75, so when it started leaking I considered it disposable and just threw it away).

Bill Robertson
#5939

[Henrik]

Looking for a A/C compressor. Any help?:confused0:

Here are your options:
1) Buy a NOS stock SD510 compressor from DMCx.
2) Buy my used, stock SD510 compressor. $50 + shipping.
3) Buy a SD7H15QD4708.

All of the above are drop-ins.

Just curious: What are the symptoms leading you to believe the compressor is bad?

[WHO1DMC]

Well it happened coming back from the Springfield convention. Herd a little sgueal it got louder and then looked back seen the white cloud of smoke and it squeals every time I turn it on, must be gest enough left to engage the clutch

[content22207_2]

If you can live with a Made in China knockoff, this one will probably end up less than $100: http://www.ebay.com/itm/SD508-Polished-Sanden-type-8-rib-serpentine-compressor-new-in-box-street-show-/401158779822?hash=item5d66ed33ae:g:WeIAAOSwRgJXk5A 3&vxp=mtr (you'd need to swap both the back plate and the pulley).

Bill Robertson
#5939

[Henrik]

Well it happened coming back from the Springfield convention. Herd a little sgueal it got louder and then looked back seen the white cloud of smoke and it squeals every time I turn it on, must be gest enough left to engage the clutch

As a very basic sanity check: With the engine off, grab the armature (front) plate of the compressor and turn it by hand. If it's smooth with little resistance, then it's probably OK.

Next, with the engine running and compressor turned on: Is the squeal due to a loose/slipping belt?

If there is lots of trauma, i.e. smoke and screech and such: Is the armature plate turning at the same rate of speed as the rotor? If not, then the compressor clutch slippage may be due to excessive air gap between the compressor's armature plate and the rotor. This can be adjusted by removing a few shims.

The Sanden compressor is relatively durable; trying to get you to not jump to conclusions....

[David T]

As a very basic sanity check: With the engine off, grab the armature (front) plate of the compressor and turn it by hand. If it's smooth with little resistance, then it's probably OK.

Next, with the engine running and compressor turned on: Is the squeal due to a loose/slipping belt?

If there is lots of trauma, i.e. smoke and screech and such: Is the armature plate turning at the same rate of speed as the rotor? If not, then the compressor clutch slippage may be due to excessive air gap between the compressor's armature plate and the rotor. This can be adjusted by removing a few shims.

The Sanden compressor is relatively durable; trying to get you to not jump to conclusions....

Good advice! Also check the 2 idler bearings. The A/C compressor is pretty rugged. It dies because of abuse. Not enough oil because the system leaks and after many "Top-Offs" all of the oil is gone or the system is overfilled or contaminated.

[WHO1DMC]

Well it might not be the bearings but worse. I can turn it but not all the way around part way you can hear a little click then dead stop.

[DMCMW Dave]

Well it might not be the bearings but worse. I can turn it but not all the way around part way you can hear a little click then dead stop.

Broken internal parts (the compressor equivalent of a broken connecting rod). Time for a replacement.

[content22207_2]

The A/C compressor is pretty rugged. It dies because of abuse.

Not always -- they also die because the front seal wears out (just like a water pump, crankshaft, or axle seal wearing out). No abuse -- just lots and lots of use (shaft spinning in the seal). Has happened to me twice over the years.

Just like a water pump weeping coolant, the compressor weeps oil and refrigerant out the front. Tell tale sign is a band of oil slung against the driver side pontoon and across the engine cover. And you keep losing freon.

Bill Robertson
#5939

[Henrik]

Broken internal parts (the compressor equivalent of a broken connecting rod). Time for a replacement.

Yes, if those are the symptoms then it's due for an immediate replacement. Once a compressor goes - it GOES and may shoot crap all throughout the system.

[Bitsyncmaster]

A/C bearings went out, squeal smoke and :sad30: looking at the sd7 or sd508 compressors. Looking for the least drage on the engine. Any thoughts or piont outs to other posts?

Thanks Dave

I've been using an SD5H14 for 8 years and it seems to work fine. It has a little less displacement so less engine load. I still get 42 deg. most of the time from the center vent. I run R134a with PAG oil. I had to swap the back plate from the original compressor.

[Henrik]

... so less engine load.

On that subject, my VR6 engine just happened to be equipped with Sanden's variable displacement compressor, SD7V16. An excellent pump that we developed mainly for VW during my Sanden years. This compressor has the advantage of a) no clutch cycling and b) optimal (minimal) engine drag during low load conditions due to the fact that it automatically adjusts to a lower flow rate.

It's entirely possible to use this compressor on the PRV but I doubt it exists with a V-belt clutch and a QD head. Not sure if it exists in ear mount config either. Some research required.

[Chris4099]

I've been using an SD5H14 for 8 years and it seems to work fine. It has a little less displacement so less engine load. I still get 42 deg. most of the time from the center vent. I run R134a with PAG oil. I had to swap the back plate from the original compressor.

I've been using this compressor as well (from specialtauto.com) and am very happy with it. It is slightly less powerful, but still capable of cooling the interior. Just has longer cycle times with less drag on the engine as well. Between it and the low current fans, there is no impact on the feel of the car while driving. I have to use a monitoring light I set up to tell when it's actually cycling.

[dn010]

Off topic a bit, what would be the symptoms of a VOV installed the incorrect direction? I'm having a bit of compressor issues and am wondering if that could be a cause.

Edit: I guess it would be nice to describe my issues - compressor will work fine and air will be cold with low amount of R134. When trying to top off to proper amount, compressor clunks/chugs and it WILL stop the engine if I keep trying to put the correct amount in. I did empty/fill it with the correct amount of Ester oil prior to filling with refrigerant. This is the stock compressor and I never had issues prior to this.


On that subject, my VR6 engine just happened to be equipped with Sanden's variable displacement compressor, SD7V16. An excellent pump that we developed mainly for VW during my Sanden years. This compressor has the advantage of a) no clutch cycling and b) optimal (minimal) engine drag during low load conditions due to the fact that it automatically adjusts to a lower flow rate.

It's entirely possible to use this compressor on the PRV but I doubt it exists with a V-belt clutch and a QD head. Not sure if it exists in ear mount config either. Some research required.

[SS Spoiler]

Are you putting in liquid or gas?

[content22207_2]

Are you adding the freon as a gas or as a liquid (can/canister right side up or upside down)? Adding as a liquid is hard on the compressor -- it's designed to pump gas, not liquid.

Bill Robertson
#5939

[Bitsyncmaster]

Off topic a bit, what would be the symptoms of a VOV installed the incorrect direction? I'm having a bit of compressor issues and am wondering if that could be a cause.

Edit: I guess it would be nice to describe my issues - compressor will work fine and air will be cold with low amount of R134. When trying to top off to proper amount, compressor clunks/chugs and it WILL stop the engine if I keep trying to put the correct amount in. I did empty/fill it with the correct amount of Ester oil prior to filling with refrigerant. This is the stock compressor and I never had issues prior to this.

I tried the VOV in my DeLorean and because of a bend in the pipe where it installs and it made the VOV valve fail closed.

[dn010]

It was added with a typical refill can from a parts store, can turned upside down once pierced.

Can turned upside down & shaking was per the print on the can, is it supposed to be done right-side up?


Are you putting in liquid or gas?

[dn010]

I tried the VOV in my DeLorean and because of a bend in the pipe where it installs and it made the VOV valve fail closed.

Did you notice this immediately while installing or did you install it and run it like this? If so, symptoms?

[content22207_2]

It was added with a typical refill can from a parts store, can turned upside down once pierced.

Can turned upside down & shaking was per the print on the can, is it supposed to be done right-side up?

Is your low side dropping to ~30 PSI? If so, you can add the freon as a gas. Try it with the can right side up and see if the compressor is happier.

What are your high side readings?

BTW: Wally World has R134 for $4.88 a can.

BBTW: I find my system cools better with the low side switch set to ~25 PSI. There's a straight blade screw between the terminals to adjust the switch. Can't remember which direction, but it will be obvious if you use a low side gauge.

Bill Robertson
#5939

[dn010]

I should have done a better job specifying - I add the cans rotating them from upside down/up & shaking it, not just leaving it upside down.

Thanks for the info Bill, I actually did get my 134 from there! I don't recall my low side or high side numbers, I can run my system tonight and find out. It seems mine liked the lower pressures as well so that might just be all it is. Maybe I'll get a new low pressure switch from Autozone and do some adjusting tonight.

[Bitsyncmaster]

Did you notice this immediately while installing or did you install it and run it like this? If so, symptoms?

It was noticed when charging the system. The compressor would shut off for a long time because it would pull below 30 lbs and take a long time to rise.

[Bitsyncmaster]

I should have done a better job specifying - I add the cans rotating them from upside down/up & shaking it, not just leaving it upside down.

Thanks for the info Bill, I actually did get my 134 from there! I don't recall my low side or high side numbers, I can run my system tonight and find out. It seems mine liked the lower pressures as well so that might just be all it is. Maybe I'll get a new low pressure switch from Autozone and do some adjusting tonight.

When you charge with small cans, you put the can in hot water keeping the can upright. That way you keep a good gas pressure and it charges quickly.

[content22207_2]

When you charge with small cans, you put the can in hot water keeping the can upright. That way you keep a good gas pressure and it charges quickly.

Just let the can hang down next to the exhaust manifold. Much easier and works just as well.

Bill Robertson
#5939

[WHO1DMC]

I'm a total believer in you pay for what you get. But do the off brand style compressors have a similar performance or is it a longevity thing?


Thanks Dave B.

[Henrik]

I'm a total believer in you pay for what you get. But do the off brand style compressors have a similar performance or is it a longevity thing? Thanks Dave B.

I spent 11 years with Sanden's Compressor Engineering Department, first as an application engineer, then project engineer and finally lab manager. The requirements (ie durability, performance, noise, weight and cost) that their compressors have to meet are astounding. Where else would you run a compressor at 6,000 RPMs, 450 psig discharge pressure and fast clutch cycling for hundreds of hours (this combination of conditions would not exist in real life) Nevertheless, since I left the Chinese knock-offs have cropped up and needless to say they have made some pretty darn good copies.

[content22207_2]

I wonder if you could rig up a high side filter screen so if a Made in China compressor starts blowing itself apart it won't pollute the whole system? They're cheap enough to be disposable items just like brake shoes. If I knew they couldn't pollute the rest of the system I'd buy one without hesitation.

Bill Robertson
#5939

[WHO1DMC]

What oils are best for a 134a system? For instance pag 46. Doing a back cover swap. Do you just have to change the seals like orings or are there internal parts as well?

Thanks Dave B

[dn010]

I use ester oil readily available at any parts house.

Sent from my XT1254 using Tapatalk

[content22207_2]

Ester is universally compatible with both mineral oil and PAG. If you pull a vacuum before refilling there shouldn't be any residual R12. You could well have residual mineral oil, especially if the system isn't flushed. Easter is compatible with residual mineral spirits if you use that as flushing fluid.

To be brutally honest I don't see any reason to use PAG.

Bill Robertson
#5939

[DMCMW Dave]

To be brutally honest I don't see any reason to use PAG.

Bill Robertson
#5939

Agree! Ester (POE) is the universally compatible oil. You need to be careful with the small R134 cans and be sure not to buy them with the oil already in the can, because that will be PAG.

[Ron]

Agree! Ester (POE) is the universally compatible oil. You need to be careful with the small R134 cans and be sure not to buy them with the oil already in the can, because that will be PAG.Dave, I'm not sure what you mean by small cans (3/10/12 oz...tank ;-), but in case it helps, Interdynamics offers 2 oz (EC-2) and 8.5 oz (INTEEO-6) cans of Ester oil (plus 2 oz 134a) and Quest has 2+1...

[Ron]

$.02

I can see using POE/134a (and sometimes do), but you have to be careful with the time the system is open and how clean it is. Basically they call for 15 min max total open system time because it absorbs moisture ~100 times faster (some claim a lot faster) and you can't remove it by simply vacuuming the system. You have to remove it with a desiccant (molecular sieve best) or go through several cycles of vacuuming it down and flowing in nitrogen if saturated (3 to 4 times -- a PITA). They have found that it acts like a detergent. When retrofitting, if a HIGH quality flushing agent is not used, properly, it often causes contaminants to turn loose and collect, clogging the orifice, etc...

But then I have seen people adding a can of 134a to an otherwise untouched, leaky R12 system and get away with it for years. Others helped put my kids through school...

P.S. Anyone interested in an OLD Snap-On R-12 reclaim station PM me.

[Bitsyncmaster]

I have read that PAG is more hygroscopic than Ester. I have also read the opposite.

Most of my reading says PAG is the better lubricant but Ester is used for retrofit of R12 systems because Ester will mix with trace amounts of mineral oil.

If your installing a new compressor, use what the manufacture recommends an thoroughly flush the rest of your system. As always install a new accumulator (which has the dryer inside).

You can not remove the absorbed moisture from the dryer or oil via vacuum. You need to heat bake to remove the moisture.

[David T]

I have read that PAG is more hygroscopic than Ester. I have also read the opposite.

Most of my reading says PAG is the better lubricant but Ester is used for retrofit of R12 systems because Ester will mix with trace amounts of mineral oil.

If your installing a new compressor, use what the manufacture recommends an thoroughly flush the rest of your system. As always install a new accumulator (which has the dryer inside).

You can not remove the absorbed moisture from the dryer or oil via vacuum. You need to heat bake to remove the moisture.



On old "trick" we used to use, when we couldn't get a dryer, we would pull a vacuum and heat the dryer up with a torch. It seemed to work but it was hard on the paint. I have seen all kinds of things done and oftentimes it seems to have worked. I don't know for how long though. I have also seem systems filled with "black death" a thick, gooey black ooze that you can't seem to clean out. Steam won't do it, solvents won't do it, the only method was complete replacement. I still recommend staying with the original R-12 system. That is what it was designed for and that is the only stuff that works the best. As long as R-12 is available, even if it is expensive, it is the best option. Next choice would be one of the many drop-in replacements like R-141a. Switching to -134 would be my last choice. Much higher pressures, less capacity, and you have the incompatibility problem with the oil.

[Bitsyncmaster]

[/B]

On old "trick" we used to use, when we couldn't get a dryer, we would pull a vacuum and heat the dryer up with a torch. It seemed to work but it was hard on the paint. I have seen all kinds of things done and oftentimes it seems to have worked. I don't know for how long though. I have also seem systems filled with "black death" a thick, gooey black ooze that you can't seem to clean out. Steam won't do it, solvents won't do it, the only method was complete replacement. I still recommend staying with the original R-12 system. That is what it was designed for and that is the only stuff that works the best. As long as R-12 is available, even if it is expensive, it is the best option. Next choice would be one of the many drop-in replacements like R-141a. Switching to -134 would be my last choice. Much higher pressures, less capacity, and you have the incompatibility problem with the oil.

You would not want to heat the accumulator if it has any oil in it.

[DMCMW Dave]

You would not want to heat the accumulator if it has any oil in it.

You should. It be heating it that hot. You don't want to melt the desiccant bag.


Sent from phone

[Bitsyncmaster]

You should. It be heating it that hot. You don't want to melt the desiccant bag.


Sent from phone

I rejuvenate my desiccant that I store some electronic components with by baking them in an oven at 250 deg/F for about one hour. I know it works because I have humidity sensor cards stored with those components. The sensor cards also rejuvenate at that temp.

[Ron]

I can see your sensor showing that afterwards, but we were taught that most of the moisture would remain in the desiccant since the moisture combines with it (using it up)...and that you would damage the sack if you got it all hot enough to separate. But, things may be different nowadays...

[content22207_2]

Switching to -134 would be my last choice.

Puts you in a very small minority.

R134 is the de-facto conversion choice of nearly every owner of every vehicle make. That's why all parts houses -- even Wally World -- sell R12 to 134 conversion fittings, no matter how flimsy (NAPA's conversion fittings are the only ones worth a damn IMHO).

It is true that R134 has a slightly warmer boiling point -- negative 16 degrees versus negative 22 degrees for R12. But when it's 100 degrees outside, are you really going to notice negative 6 degrees difference? Conventional wisdom is overall system loss is 10%. Don't know how accurate that is, but let's assume it is 100% accurate -- vent temps go from 40 degrees to 44 degrees. Small price to pay for freon at $4 a can. 44 degrees feels pretty darn good when it's 100 degrees outside (IMHO).

Bill Robertson
#5939

[Ron]

Conventional wisdom is overall system loss is 10%. Don't know how accurate that is, but let's assume it is 100% accurate -- vent temps go from 40 degrees to 44 degrees. Small price to pay for freon at $4 a can. 44 degrees feels pretty darn good when it's 100 degrees outside (IMHO).

Bill Robertson
#5939
+1

Not to mention that there is not a lot of field data out on other refrigerants, yet.
And with 134a, the only solution offered to compensate is a 30% larger condenser....Um, No!

[Morpheus]

+1

Not to mention that there is not a lot of field data out on other refrigerants, yet.
And with 134a, the only solution offered to compensate is a 30% larger condenser....Um, No!

Wouldn't the newer, parallel flow condenser now offered by DMCH overcome this limitation?

https://store.delorean.com/p-7716-condenser-includes-accumulatordrier-orifice-tube-and-o-rings.aspx
(The picture shows the older, NOS serpentine condenser but the description is for 134a.)

[WHO1DMC]

When doing a back plate transfer do you just have to change the o rings or is there more to it? sd5h14 style

Thanks Dave B.

[content22207_2]

Back is sealed with a metal gasket. They are available individually all over the Internet if you want to replace it. I've never had any problem reusing the one that comes with the compressor.

O rings on your current back will have been compressed, so I'd definitely change them. Only 30 cents apiece from a hardware store (I think Houston wants a buck apiece). I'm using square profile O rings from McMaster: http://www.mcmaster.com/#4061t233/=13jjnad (also available in Viton and silicone).

Bill Robertson
#5939

[content22207_2]

+1

Not to mention that there is not a lot of field data out on other refrigerants, yet.
And with 134a, the only solution offered to compensate is a 30% larger condenser....Um, No!

1234YF (supposed replacement for R134) is now available for $1,000 per 10 lbs canister (no joke -- look it up).

I promise you: properly installed, R134 provides all the cold air you could ever ask for. I use it in all my vehicles, including the school bus (originally R12).

Bill Robertson
#5939

[David T]

1234YF (supposed replacement for R134) is now available for $1,000 per 10 lbs canister (no joke -- look it up).

I promise you: properly installed, R134 provides all the cold air you could ever ask for. I use it in all my vehicles, including the school bus (originally R12).

Bill Robertson
#5939

The 10% loss in cooling capacity is directly related to the fact that you can only put 90% as much -134 in as compared to -12. That is to keep the head pressures low enough so you won't blow the relief valve. System cooling capacity is directly related to the mass of the refrigerant since that is what is transferring the heat. Less refrigerant = less heat flow. The high head pressures are because you have too small a condenser coil for -134 so it comes out hot and at high pressure. R-134 also needs higher pressures to liquefy. Cooling capacity is based on heat transfer and you can get only so much per pound of refrigerant. The "rule of thumb" is 12,000 BTU's per 1 LB of refrigerant. So you see if you have less refrigerant to transfer heat your system is not going to have the same capacity as a system that can handle more refrigerant. That is where the loss in capacity comes in. It is most noticeable when the system is under the greatest load, ie, you won't notice the loss of capacity if you are not using the system TO capacity. Practically it means it will take longer to bring the cabin temperature down to a desired level.
The other problem is refrigerant oil compatibility. The oil used for R-12 is incompatible with the oil used for -134. If you were to mix the oils you get a black gooey substance that will plug up the system. If you do not change the oil it won't properly lubricate the system. It is almost impossible to get ALL of the old oil out of the compressor so you are now faced with a bad choice.
For both these reasons it is best to stay with R-12. Since you are using so little (2.2lbs) you aren't spending a lot of money staying with -12. The tip is to make your system as leaktight as you can so you don't have to "top off" all the time. I have years of experience with drop-in replacements and you still lose capacity more or less, the only good things about them is you don't have the oil compatibility problem and they are a little less expensive than R-12. For those of you who have a leaky system and have to top off every year, there are now good additives you can put into a system that can plug small leaks. Easy to use. I also suggest a dye to find any leaks. If you DO change to -134 you are supposed to change the service ports and put a label on the system noting the change of refrigerant AND the correct weight of charge. In all cases you should change the accumulator/dryer and vacuum the system out to 400 microns before adding the refrigerant. As per Service Bulletin ST-29-11/81 the refrigerant charge was changed form 2.75 LBS to 2.2 LBS. That is with R-12. Adjust accordingly for -134.
Before doing any A/C work you should inspect and test drive the car to make sure the engine cooling system is working 100%. You will never get good A/C if you have any problems with the engine's cooling and you will overwork it to the point where you can overheat the motor. Seal up any holes in the cabin to prevent outside air leakage. Make sure the ducting inside the doors is not leaking or you can lose a LOT of cold air inside the doors. Check the boot on the center vents to make sure it is properly and completely sealing the center vents. Make sure the mode switch is not hissing and moving all of the actuators properly. Getting the A/C right is one of the more complex things in a car, it involves a lot of other systems and if any of them aren't working right you won't get all of the A/C you should.
Other notes for those of you still thinking about changing to -134. You must remove and drain as much of the oil as you can from the compressor and then refill with the proper amount. You MUST replace the dryer/accumulator and all 3 hoses and all of the seals. You must flush the evap and cond coils. When pulling a vacuum it is "good practice" to use a heat gun on the dryer and when filling and testing you should have a fan in front of the car to provide air. With -134 you should adjust the low pressure switch to set the cycling properly. Check that you have the uprated circuit breakers for the cooling fans and the cabin fan. Inspect the fuseblock and relay area for any signs of heat damage. A LOT to do to get good, cold A/C!!!!!!!!!!!!! And you need a lot of special tools and must know how to use them. That is why most people will just send the car out and have it done. Who knows if they did a thorough job? There is a whole lot more to this than just squirting in some gas!

[content22207_2]

there are now good additives you can put into a system that can plug small leaks

Do those additives do as good a job plugging up the orifice tube as cooling system additives do plugging up radiator and coolant passages? (Or engine oil additives do plugging up oil passages).

I periodically flush my system backwards just to ensure the orifice tube remains clear -- I respectfully decline any additives.

Bill Robertson
#5939

[Ron]

Wouldn't the newer, parallel flow condenser now offered by DMCH overcome this limitation?

https://store.delorean.com/p-7716-condenser-includes-accumulatordrier-orifice-tube-and-o-rings.aspx
(The picture shows the older, NOS serpentine condenser but the description is for 134a.)
I don't know if it's performance is 30%> No stats and I haven't had the pleasure replacing one on a D.
...If I needed one, I would scrounge for a known good one...probably order a serpentine from MW and know it would work out.

[Ron]

1234YF (supposed replacement for R134) is now available for $1,000 per 10 lbs canister (no joke -- look it up).

I promise you: properly installed, R134 provides all the cold air you could ever ask for. I use it in all my vehicles, including the school bus (originally R12).

Bill Robertson
#5939Then I hope you don't have the type where refrigerant actually goes through the roof. :clown:

[content22207_2]

OEM school bus A/C is piped under the floor, with condensor units mounted in the side skirts. Evaporator units are of course mounted by the ceiling. Self contained roof top units are private owner installs on non A/C buses, often stuck through the roof top emergency exit openings.

Bill Robertson
#5939

[WHO1DMC]

For 134a how much does it take to fill a D.

[Morpheus]

For 134a how much does it take to fill a D.


A/C Refrig. Charge: R12: 2.2 lbs (35.20oz), R134a: 1.98 lbs (31.68oz)

[David T]

Do those additives do as good a job plugging up the orifice tube as cooling system additives do plugging up radiator and coolant passages? (Or engine oil additives do plugging up oil passages).

I periodically flush my system backwards just to ensure the orifice tube remains clear -- I respectfully decline any additives.

Bill Robertson
#5939

I have not had any problems yet using leak stopping additives blocking an orifice tube. There is a screen on it to stop debris from plugging up the orifice. I see no need for periodic flushing if you have a clean, uncontaminated system. BTW, some people have reported using a VoV instead of an orifice tube and claim good results especially with -134. I have no experience with it so I can't confirm good or bad. Sounds like a good idea and could be a way to get a little more -134 into the system. The biggest problem I see is you have to remove the orifice tube to install the VoV with the high probability of damaging the pipe.

[dn010]

I am using a VOV with R134 and have nice cold air. I know others here who have had issues with them though.


I have not had any problems yet using leak stopping additives blocking an orifice tube. There is a screen on it to stop debris from plugging up the orifice. I see no need for periodic flushing if you have a clean, uncontaminated system. BTW, some people have reported using a VoV instead of an orifice tube and claim good results especially with -134. I have no experience with it so I can't confirm good or bad. Sounds like a good idea and could be a way to get a little more -134 into the system. The biggest problem I see is you have to remove the orifice tube to install the VoV with the high probability of damaging the pipe.

[content22207_2]

For 134a how much does it take to fill a D.

I use 2 cans (about $10). Pressures are fine. My low side switch is set slightly below 25 PSI, so the high side is slightly higher than it would be at 28 PSI, but it still stays within specs (around 300 PSI on a hot day).

Bill Robertson
#5939

[Bitsyncmaster]

I use 2 cans (about $10). Pressures are fine. My low side switch is set slightly below 25 PSI, so the high side is slightly higher than it would be at 28 PSI, but it still stays within specs (around 300 PSI on a hot day).

Bill Robertson
#5939

By the way, Walmart is now selling a can of R134a at $4.88 everyday price.

I usually charge from a 30 lb bottle until the high side pressure is about 250 PSI with the the engine RPM about 2500. You can also measure the temp from the vent and when it stops dropping colder you have enough charge.

[Ron]

A/C Refrig. Charge: R12: 2.2 lbs (35.20oz), R134a: 1.98 lbs (31.68oz)
+1

[David T]

By the way, Walmart is now selling a can of R134a at $4.88 everyday price.

I usually charge from a 30 lb bottle until the high side pressure is about 250 PSI with the the engine RPM about 2500. You can also measure the temp from the vent and when it stops dropping colder you have enough charge.

Very commonly used method but very inaccurate. You should either use a charging cylinder or a scale.

[content22207_2]

Very commonly used method but very inaccurate. You should either use a charging cylinder or a scale.

Kind of defeats the purpose of a manifold gauge set (the middle port is what you connect to a freon canister. Knobs on either side are valves that open/close high and low sides to the canister).

Watch an A/C tech sometime. They weigh the canister on the truck, fill the system just as Dave McKeen suggested (watching high and low side pressures on the manifold gauges), re-weigh the cylinder on the truck, then write a bill for the difference.

Bill Robertson
#5939

[content22207_2]

By the way, Walmart is now selling a can of R134a at $4.88 everyday price.

I usually charge from a 30 lb bottle until the high side pressure is about 250 PSI with the the engine RPM about 2500. You can also measure the temp from the vent and when it stops dropping colder you have enough charge.

Yea, I picked up a 30 lbs canister over the winter because everyone predicted R134 prices would spike this summer. Then the bottom fell out....

If it's 95-100 degrees outside my high side usually runs around 300 PSI (engine rev'ed).

Bill Robertson
#5939

[Ron]

???


I usually charge from a 30 lb bottle until the high side pressure is about 250 PSI with the the engine RPM about 2500.
*The clutch should cycle out before 250 PSI unless the ambient is greater than 110F!

Don't you have a scale?


If it's 95-100 degrees outside my high side usually runs around 300 PSI (engine rev'ed).
*At 100F the clutch should cycle out at 190-230 PSI.

=======

*These are for R12 -- 134a would be a bit higher, but whew...

See N:09:01

[content22207_2]

http://i206.photobucket.com/albums/bb29/Tran2la/74%20Chevy%20Nova/R134aTemp-pressure-chart.jpg

My bus runs closer to 250 PSI, but it's got expansion valves that won't drop the low side below 30 PSI. Last time I put the gauge set on my DeLorean the low side switch was dropping to about 23 PSI. The lower the low side drops, the higher the high side rises.

And last weeks temps were hovering right around 100....

Bill Robertson
#5939

[content22207_2]

It really is tiresome to keep taking pictures to prove Ron wrong. Outside temp 83 degrees:

45086

Bill Robertson
#5939

[content22207_2]

To anyone wondering the efficacy of R134, I assure you -- it does work:

45087

(R134 may have theoretical shortcomings on paper, but in the real world it works just fine).

Bill Robertson
#5939

[DMCVegas]

To anyone wondering the efficacy of R134, I assure you -- it does work:

R-134a does work very well indeed. As per EPA retrofit recommendations (which they do not officially endorse because of liability), the Low Pressure Switch does need to be adjusted counterclockwise to cycle off @ 21PSI to maximize cooling efficiency. The VOV is a sort of workaround on that adjustment.

The only other modification needed for the average R-12 system aside from the standard retrofit is the requirement for an electric radiator fan to be installed. Not a problem on the DMC-12, but you would need to remove the thermal clutch fans from older cars.

Here is a copy of the old EPA guide which they took down off of their site since R-1234yf appeared:

-------------------------------------------------------------------------------------------------------------------

One Shop's Experience Retrofitting Motor Vehicle Air Conditioners to HFC-134a


OZONE PROTECTION HOTLINE TOLL-FREE (800) 296-1996
Many technicians are looking for the proper procedures to retrofit vehicles to R-134a. Although EPA does not have the technical expertise to recommend procedures for each vehicle that may require retrofitting, here are some recommendations from one service facility and parts wholesaler, Arctic Auto Air in Fort Lauderdale, Florida, that has been recognized as a pioneer in retrofitting.

This information is being provided solely as a service to automotive technicians, who should rely on their experience and judgment to determine the most appropriate steps in retrofitting each vehicle that comes into a shop, whether the new refrigerant is HFC-134a or another substitute. Neither EPA nor Arctic Auto Air warrants or guarantees any of this information. EPA has not tested any of these procedures and does not endorse them. Technicians may discover that this information contradicts other information provided to them by automakers or by suppliers. Nevertheless, EPA believes technicians may find it valuable to see the recommendations of one shop that has completed over 1,000 retrofits.

Arctic Auto Air's Retrofit Procedures

1. Recover the R-12 according to SAE J1989 standards.
2. If the system is contaminated, perform closed-loop flushing.

3. After any necessary parts replacement, add a PAG or ester oil to whatever exact specs the automaker recommends for mineral oil. Too much oil will affect the performance of the system.

4. If you have not already done so as part of the repair, replace the accumulator or drier -- make sure that you use an R-134a-compatible desiccant such as XH-7.

5. Install the R-134a service ports. Remember that depending on the design of the ports, you may have to remove or replace the schraeder valve cores. The service ports for R-12 are the opposite for R-134a: the large port is on the discharge side and the small port is on the suction or low side.

6. Evacuate the system for 45 minutes after it reaches 29.5 inches of vacuum. A retrofit requires longer evacuation time to ensure removal of the residual R-12.

7. Charge the system with R-134a using a calibrated charging cylinder or weighing scale.

8. The retrofit will generally require an R-134a charge that is equal in weight (# of ounces) to between 75 and 90% of the original R-12 charge. Start with an R-134a charge that is equivalent to 75% of the recommended R-12 charge. If there is excessive clutch cycling, add up to 5% increments of R-134a. Do not exceed 90%.

9. Leak check vehicle.

10. Fill out and apply retrofit label over original R-12 label.

11. Test drive vehicle.

12. Do a performance check. High-side pressures should be within 10-15% of established R-12 pressures.


More Tips from Arctic...

On most vehicles, the duct temperatures of R-134a versus R-12 are generally the same. On some vehicles, the duct temperature is colder by a few degrees and in some instances on rear wheel drive domestic vehicles, the duct temperature may be 2-4 degrees warmer at idle.
The high-side pressures at idle generally remain the same on front wheel drive vehicles with dual electric fans. High-side pressures at an idle are sometimes higher in rear wheel drive vehicles by approximately 10-15%. However, this increase in pressure should not affect the performance or durability of the system.

General Motors

On clutch cycling orifice tube systems, adjust the cycling switch counter clockwise to 21 psi cycle off.

On full size front wheel drive vehicles with a single engine cooling fan, an auxiliary electric cooling fan may be needed.

On smaller front wheel drive vehicles, the single engine cooling fan is adequate.

On 1988 to 1992 Cadillacs, replace the low temperature evaporator sensor. This will alleviate a false reading of codes 46-47, which means low inlet evaporator temperature, rapid cycling or plugged orifice tube.

On rear wheel drive vehicles, as long as the fan clutch and cooling system are operating well, only adjustment of the cycle switch is required.

Chevy Suburbans with single air may need an auxiliary electric cooling fan. On full size vans and Suburbans with dual air, add an electric auxiliary cooling fan.

Ford

On vehicles with clutch cycling orifice tube systems, adjust the cycling switch counter clockwise to 21 psi cycle off. Full size Broncos and vans may need an electric auxiliary cooling fan.

On pickups without heavy duty cooling packages, an electric auxiliary cooling fan may be needed.

On rear wheel drive vehicles, as long as the fan clutch and cooling system are in good operational condition, only the adjustment of the cycle switch is required.

On Aerostars, when a leaking condenser replacement is necessary, replace with a new motorcraft YJ351 multiflow condenser.

Chrysler

On rear wheel drive vehicles with a thermostatic switch, no adjustments or modifications are needed.

On Caravans and Voyagers with single air and without pressure cycling switches, no adjustments or modifications are necessary.

On vehicles equipped with variable displacement compressors, no adjustments or modifications are necessary.

On front wheel drive vehicles with thermostatic switches and a two blade engine cooling fan, an auxiliary electric cooling fan will be needed.

On vehicles with pressure cycling switches, rapid cycling occurs due to the lower evaporator pressure. These switches are not adjustable. However, they can be replaced with an adjustable thermostatic switch which is secured at the outlet of the evaporator. Install a low pressure protection switch into the expansion valve and wire these two switches in series.

On Caravans and Voyagers with dual air, due to the lack of condenser cooling capacity, stay with R-12.

Imports

On early model Toyotas and Nissans with POA valve systems, the evaporator pressure is lower with R-134a. Adjustment of the POA valve is required. Turn the pressure regulator adjustment screw approximately one quarter turn counter-clockwise.

On Mercedes that do not have auxiliary condenser fan switches that close at approximately 225 psi, replace the switch with a switch that does close at that psi. All other vehicles require no adjustment or modification.

[content22207_2]

17-18 PSI on the low side is a tad low (look at my low side gauge). That is flirting with ice formation. I added a few puffs from a 30 lbs canister which brought it back to the low 20's (engine rev'ing -- notice my foot on the accelerator pedal).

Bill Robertson
#5939

[David T]

The "proper" way to charge a system with refrigerant is to fill a charging cylinder with the appropriate amount of liquid refrigerant and then put that amount into the system. The other way is to weigh the cylinder before filling the system, calculate the difference to get the right fill and then fill the system till you reach the calculated weight. Less accurate because of the hoses, some liquid is still in the hoses so you wind up slightly overfilling.These procedures both assume an empty system (no refrigerant to start with). Any other method would be used to "top off" a system that is undercharged, usually because of leaks. Weighing the cylinder as Bill says is only for billing purposes. Theoretically they should only be charging you for what the system says a fill is. In the case of a Delorean 2.2 lbs if your system was completely flat to begin with. When was the last time you saw anyone use a charging cylinder to fill a system? Nowadays I only see it used in very small systems like window units and refrigerators that have very small amounts of refrigerant and the fill is critical to proper operation because they use capillary tubes (kind of like the orifice tube we use in a Delorean). Since Deloreans do not use an expansion valve they are very sensitive to the correct fill. Most techs will overfill figuring a leaky system. That keeps the system working a little longer but at a loss of efficiency. As the refrigerant leaks out the system will get colder and colder before it starts to get warmer and then stops.
No one said -134 won't work, it just provides less system capacity and has incompatibility problems with the original oil that was used with -12. You cannot measure capacity by measuring the temp of air coming out of the evap coil. If you let it get too cold it will just freeze up so you never want air coming out lower than about 38 degrees. That is one reason why the compressor cycles, it is kind of like a defrost, allowing any ice that may have accumulated on the evap coil to melt. The main purpose of the low pressure switch, to keep the evap coil temp (pressure) above 38 degrees.

[Bitsyncmaster]

???


*The clutch should cycle out before 250 PSI unless the ambient is greater than 110F!

Don't you have a scale?


*At 100F the clutch should cycle out at 190-230 PSI.

=======

*These are for R12 -- 134a would be a bit higher, but whew...

See N:09:01

I never see the clutch cut out when charging. There just is not enough air moving over the condenser to get the low pressure to cut out.

[Ron]

It really is tiresome to keep taking pictures to prove Ron wrong. Outside temp 83 degrees:

45086

Bill Robertson
#5939
Just when I thought you were settling down... :facepalm:

==-===

I don't see how -- We must be on different pages here...

For R12 at 100F, if you revv the engine and take the readings when the clutch cycles out, you should read 189-230 PSI on the High side and 25-33 PSI on the Low side. (N:09:01). But as I said, 134a will be a bit higher.
You said you were getting about 300, or 70 PSI higher... Not too surprising, now that I know you were at 100F and have a VOV.

I can't read the gauges in your pic.
FWIW at 80F (~83), R12 should give: 145-190 High, 25-32 Low, when the clutch cycles out.

If it works for you, great!

[Ron]

...
Here is a copy of the old EPA guide which they took down off of their site since R-1234yf appeared:
...
+1

I'm 100% with everything but the electric fan...which I assume is what the 30% larger condenser is about...

[Ron]

The "proper" way to charge a system with refrigerant is to fill a charging cylinder with the appropriate amount of liquid refrigerant and then put that amount into the system. The other way is to weigh the cylinder before filling the system, calculate the difference to get the right fill and then fill the system till you reach the calculated weight. Less accurate because of the hoses, some liquid is still in the hoses so you wind up slightly overfilling..The way I do it away from the shop, say at a D meeting, I use a cheap digital (food) scale...Attach the fill tube, purge it, put it on the scale, zero it, and remove 4.32 oz. Then dump it and 2 cans in and double check the pressures as above.
12 - 4.32 = 7.68
7.68 + 12 +12 = 31.68 oz [134a]

=================

More Info (Retro, etc.) HERE (http://dmctalk.org/showthread.php?7921-AC-Pressure-Charts-Reading-Gauges-(R12-and-Retrofit))

[David T]

I never see the clutch cut out when charging. There just is not enough air moving over the condenser to get the low pressure to cut out.

When actually putting the refrigerant into the system you have to put a jumper in place of the low pressure switch. Otherwise it takes a lot longer to to fill the system. Once you have the full charge in you reconnect the switch and adjust if necessary. The Delorean was designed for use with R-12. All of the components were sized appropriately for R-12. To properly change the system to handle -134 you must change the hoses, the service ports, the oil, an orifice tube with a larger orifice (or a VoV), and replace the condenser coil with one about 20% bigger. That is if you want to maintain the same capacity as you would have using R-12. You will be running higher temperatures and pressures. All that just so you can use a cheaper refrigerant? If you are converting to -134 because you think it is more environmentally friendly, go ahead and use the R-12 but make your system leakproof so you don't waste any.

[content22207_2]

I can't read the gauges in your pic.
FWIW at 80F (~83), R12 should give: 145-190 High, 25-32 Low, when the clutch cycles out.

Pic gauges read 17-18 low and 225-230 high. I was a tad low on freon so I topped it off after the pic was taken, giving me 22-23 low and 250-260 high. Perfectly acceptable by R134 pressure charts.

Clutch cycling is controlled by the low pressure switch, which can be adjusted differently on each car.

I have a fixed orifice tube, so engine RPM (spinning the compressor) determines my pressures. Like Dave, I fill mine to give good A/C at highway RPM's. Obviously the pressures are low side high and high side low at idle and vice versa at WOT.

Bill Robertson
#5939

[Ron]

Pic gauges read 17-18 low and 225-230 high. I was a tad low on freon so I topped it off after the pic was taken, giving me 22-23 low and 250-260 high. Perfectly acceptable by R134 pressure charts.

Clutch cycling is controlled by the low pressure switch, which can be adjusted differently on each car.

I have a fixed orifice tube, so engine RPM (spinning the compressor) determines my pressures. Like Dave, I fill mine to give good A/C at highway RPM's. Obviously the pressures are low side high and high side low at idle and vice versa at WOT.

Bill Robertson
#5939Sorry, I had you mixed up with Dave on the VOV. But same difference I.E. I'm not surprised ot the 'high' pressures since I now know you were at 100F and have adjusted the switch...

I see the problem now too. You aren't reading pressures as per the manual -- Apples and peaches.
But like I said, if it works for you....

[content22207_2]

Dave's running a fixed orifice tube as well (Post #20). That's why we rev our engines to cruising RPM's to take pressure readings.

If you're getting 25-30 PSI on the low side at idle with a fixed orifice tube then the system is likely undercharged (assuming the orifice tube isn't clogged or blocked -- high side will tell). It will be cycling like crazy as the compressor speeds up.

Bill Robertson
#5939

[Ron]

Ah, I remember he was playing with them for quite a while, and assumed he fixed the bend in the pipe....reshaped it using a metal tube or ?? iirc

Every one I've seen acts like the manual calls out (~30 psi), with either type of course.

[content22207_2]

My manifold gauges show 29-30 PSI as "zero" on the R134 scale, but I find air from the evaporator is colder when the low side is low to mid 20's.

Bill Robertson
#5939

[content22207_2]

I wonder if owners unhappy with R134 just need to adjust their low pressure switch lower? (Assuming the rest of the conversion was done correctly).

Bill Robertson
#5939

[Bitsyncmaster]

I have never adjusted my low pressure switch. It's been a long time since I have charged my system but I think it cuts off around 35 PSI and on about 45 PSI. If you set it for lower pressure you may get ice forming on the evaporator. I pretty much get 42 deg. F from the center vent when driving. When I'm just sitting in the garage I get about 58 deg. F with the fan on #4, AC set to NORM. I need to drop my blower speed to see the low pressure off and on values.

I run a stock orifice. Stock condenser with Toby's fans.

My compressor (SD5H14) has a little smaller volume than the stock compressor.

I have never had to jumper the low pressure switch when charging any AC system.

[content22207_2]

I have never had to jumper the low pressure switch when charging any AC system.

If you are charging from a canister the low side will continuously pull from it as long as the manifold set valve is open, which means the low side will be ~100 PSI (varies slightly with outside temp) -- more than enough to keep the low pressure switch closed.

Bill Robertson
#5939

[Ron]

I wonder if owners unhappy with R134 just need to adjust their low pressure switch lower? (Assuming the rest of the conversion was done correctly).

Bill Robertson
#5939I would expect the high side to be too high at cut out while driving in very high ambient temps.

[content22207_2]

Depends upon the freon charge. For example, if your charge is low, and your low pressure switch is low, the low side will continue to draw down without the high side climbing, just like an expansion valve system (an expansion valve system can actually end up pulling a vacuum on the low side if the freon charge is too low).

Bill Robertson
#5939

[DMCVegas]

+1

I'm 100% with everything but the electric fan...which I assume is what the 30% larger condenser is about...

Well, you first have to realize the chemical and property differences between the two gasses of R-12 & R-134a, of which there are a few. But to put the entire thing into as simple of a perspective as possible, R-134a isn't quite as efficient as R12 when it comes to transferring heat. It's damn close, but it isn't a 100% match.

Now when you're designing an HVAC system, in this case for a car, you're going to base all of your components you engineer off of the function of the system which is dictated in large part by the type of refrigerant used. Then to a certain extent the rest of the automobile's cooling system is going to be influenced by that as well. But when the system requirements change from R-12 to R-134a, you need to either redesign the entire system, or you need to have a compromise.

So when you have a slightly less-efficient refrigerant that doesn't transfer heat as well, you need to find a way to discharge more heat from the Condenser coil to maintain the same temperatures at the Evaporator. That gets accomplished in one of two ways:

Increase CFM airflow across the Condenser Coil to remove more BTUs.
Install a larger Condenser Coil.


An electric fan can pull MORE air through the Condenser at idle, so it utilizes the full, existing cooling efficiency of the coil to maintain cooled refrigerant.

A larger Condenser however increases the amount of time the refrigerant spends cooling down since there is now a greater distance for it to travel through. So that actually increases the over all efficiency of the Condenser to maintain cooled refrigerant.

So which should you use? Well as you can see, when it came to creating guidelines for retrofitting systems with R-134a, this was pretty much the EPA's official response:

https://media.giphy.com/media/xYLRCmVZNAbCg/giphy.gif

An electric fan is more ideal since it maintains high CFM volume of air across the coils to maintain cooling while the vehicle is stationary. The fan can be engaged on the fly, and engine RPMs do not have to be increased. Thus it is more efficient. HOWEVER, installing a larger Condenser Coil is far less complicated. Especially from a manufacturing standpoint. You've spend all these R&D dollars designing a vehicle that now gets switched over to R-134a. Your choices are to abandon the designs and tooling you've already invested in for millions of vehicles which include water pumps, thermal clutch fans, & fan shrouds which have to now be dumped, and then redesign the vehicle's cooling AND electrical systems and introduce MORE parts like otterstats & additional wiring, and then retool & retrain your entire assembly line workforce just to install a couple of fans.

Or you could just make a minuscule, non-interfering parts change for a larger condenser and a couple of brackets instead. Which do you think Detroit went with?

Ideally electric fans are a better option, which is why the majority of vehicles have pretty much switched over to them now. Not all, but most.

[content22207_2]

Ideally electric fans are a better option, which is why the majority of vehicles have pretty much switched over to them now. Not all, but most.

Actually most vehicles switched to electric fans because their engines are now pointed sideways.

Bill Robertson
#5939

[DMCVegas]

Actually most vehicles switched to electric fans because their engines are now pointed sideways.

Bill Robertson
#5939

Not quite, no. What you're referring to, that would be called a transverse engine, and was done due to the lack of direct engine drive for a radiator fan.

However some, not all but some, vehicles with longitudinal engines also switched over to electric cooling fans even though the engine was still capable of driving the radiator fans.

Using Ford as an example, this would pretty much be just the passengers cars include Fox Bodies and Panthers back in the 90's that went electric when they didn't necessarily have to. So perhaps it was considerations for performance and fuel economy. However, Ford trucks still carried on with traditional radiator fans until at least 2010 with the 4th-Gen Explorer. The 11th Generation F-150 also kept it up until finally going electric in 2009 with the 12th Gen, while the F-250 and above still keep their clutch radiator fans to this day.* Of course there are also no economy concerns on these vehicles either.

*In 2006 or so, Ford started installing electrically controlled radiator fan clutches that rely upon a signal from the ECU to engage instead of radiator exhaust air temperatures. They also monitor fan speed.

[Ron]

Depends upon the freon charge. For example, if your charge is low, and your low pressure switch is low, the low side will continue to draw down without the high side climbing, just like an expansion valve system (an expansion valve system can actually end up pulling a vacuum on the low side if the freon charge is too low).

Bill Robertson
#5939Naughty, naughty -- You are changing the rules since you said, "(Assuming the rest of the conversion was done correctly)."

I'm with ya though...