Non-Functional Air Conditioning

[ccurzio]

So as many of you know, my car has had non-functional AC for as long as I've owned it. When I first bought the car, there was the all-too-familiar hiss from behind the AC panel, indicating the mode switch needed repair. The very first repair I ever performed on my car was to rebuild and reinstall that mode switch.

The problem I'm experiencing is that, regardless of setting on the mode switch, the system only ever blows hot air - except on the MAX setting. When setting to MAX, the system blows ambient air.

One thing to note is that my compressor is not getting power, but that particular issue is tabled for the time being. Before figuring out the compressor issue, it's more important to figure out why the system blows hot air on settings when it shouldn't; e.g. NORM, VENT, etc. Keep in mind that when changing modes on the mode switch, the air does blow from the correct vents based on setting, it's just that all of the air that comes out of the vents is heated.

Once I can figure out why I'm getting hot air and get that issue sorted, then we can start troubleshooting the compressor power issues.

Thanks!

[Cory W]

Have you checked the wire from the heater box to the temp knob behind the HVAC panel? I'm talking specifically about parts 8 and 12 here (http://store.delorean.com/c-365-7-3-0-electricalmechanical-controls.aspx). If you only get heated air no matter the air outlet, wouldn't it have to be the temperature control?

On my car it's in a blue sheath; I'm guessing they all are. It is bolted to the mechanicals that are operated by the knob. Unfortunately, I did not look at how it was fastened inside the box while I had my box apart a couple years ago.

[dmc6960]

Sounds like the mechanical damper which directs air through the heater core is stuck in the heating position. You get ambient air on MAX because of the hot water valve which activates on MAX shutting off coolant flow through the heater core. Does your temperature selection knob turn with resistance? Is the cable behind the knob hooked up? If those check out you'll need to follow that blue cable guide to the box to see if the damper itself is moving when you turn it.

[ccurzio]

Have you checked the wire from the heater box to the temp knob behind the HVAC panel?

I have. Turning the temperature control knob does actuate the blue wire running to the box.


Does your temperature selection knob turn with resistance? Is the cable behind the knob hooked up? If those check out you'll need to follow that blue cable guide to the box to see if the damper itself is moving when you turn it.

It does have resistance, but "normal" resistance. The cable is hooked up, and it does actuate when the knob is turned.

[Ron]

It does have resistance, but "normal" resistance. The cable is hooked up, and it does actuate when the knob is turned.
To be clear...as you turn the knob clockwise, the air does get hotter?

[David T]

The heater valve is open in all positions except MAX. Your compressor is not getting power probably because you have no refrigerant. The low pressure switch is not passing power on to the compressor. You have to find and fix the leaks, vacuum and fill the system. If you have the old (original) hoses you should probably start by ordering a new set and an accumulator/dryer. Blowing hot air in all settings except MAX with an inop A/C is normal.
David Teitelbaum





To be clear...as you turn the knob clockwise, the air does get hotter?

[ccurzio]

To be clear...as you turn the knob clockwise, the air does get hotter?

Not that I can notice, no.


The heater valve is open in all positions except MAX. Your compressor is not getting power probably because you have no refrigerant. The low pressure switch is not passing power on to the compressor.

While it wouldn't surprise me if I have no refrigerant, this is not the primary issue. Bypassing the low-pressure switch still doesn't send power to the compressor.


Blowing hot air in all settings except MAX with an inop A/C is normal.

Well this is encouraging, although I don't understand why I'd still be getting hot air on VENT.

[Ron]

+1 David


Well this is encouraging, although I don't understand why I'd still be getting hot air on VENT.The manual says the "temperature control should be turned to full cold" when in vent mode....
Sounds like all you need is to get the temp flap working to me...

[ccurzio]

Sounds like all you need is to get the temp flap working to me...

I'll bet that's a good start then. Beyond that, next step would to be to figure out why the compressor isn't getting power and then whether I have refrigerant or not.

Anyone have any idea how to test/fix that flap? That airflow box can't be easy to reach.

[Ron]

Get the flap working...the rest should be relatively easy.

Edit: I haven't had the pleasure

[ccurzio]

Well I'll be damned. I do believe, sitting in the parking lot of a King's Inn in Nashville, I just fixed my airflow box flap.

Short explanation: I'm an idiot.

Long explanation: The first time I'd started investigating this issue at any length, I'd talked briefly with Stephen and James at DMCH. The first thing Stephen suggested was to check the blue wire from the temp knob to the airflow box to make sure it's actually moving when you turn the knob. While I was on the phone with them I went to the garage, ducked into the passenger footwell, located the blue cable, and verified that it did move when you turned the temperature knob. Confused, we discussed some other things and my AC problems were again put on the back burner.

After starting this thread, I just now decided to take another look at that cable since I wasn't terribly interested in trying to pull the airflow box entirely because it's an apparent pain in the ass to reach. So I got back under there and had another look. And what do I see? something STUPIDLY OBVIOUS that I can only blame myself for missing the first time due to inadequate light and my own idiocy.

Before:
http://i.imgur.com/SlWgG.jpg

After:
http://i.imgur.com/vndfr.jpg

Me:
http://i.imgur.com/JJC10.jpg

[Cory W]

And, the rest of us:
:raveon:

Congrats on getting it done. Sometimes there's nothing more satisfying than some tiny little fix.

[Ron]

:tongue2:...I have to admit, it took me a second.
(I was thinking you meant "before" and "after" you turned the knob ;-)




Do you have a set of gauges (or an old top-off can that has one)? -- On to the compressor problem.

[ccurzio]

Do you have a set of gauges (or an old top-off can that has one)? -- On to the compressor problem.

I do not. I have absolutely no AC tools or supplies of any kind.

[dmc6960]

Do you have a set of gauges (or an old top-off can that has one)? -- On to the compressor problem.

Before tackling the charge, lets check the electrical. He said the compressor would not trip if the low pressure switch was jumped. So lets do some checks...

Low pressure switch, check for 12v along one of the leads while the ignition switch is on ACC and the mode switch set to an AC setting.

If No, check electrical connections at mode switch.
If Yes, jump switch, and check for 12v at High pressure switch if equipped (these are in serial and I dont know which direction, so you may need to reverse the order of this test).

Once you have verified 12v at both pressure switch connections and have BOTH jumped, check for 12V at compressor.

If yes, check for 12V while connected to compressor.
If no, then check for 12V at bulkhead connectors.

If compressor does not come on with 12v on lead, check voltage while it is connected to compressor. If lower than 10v, you may have a bad connection at any of the several connections up the line. At this point you can completely check the compressor by giving it direct 12v from the jump start post and a spare wire. If compressor does not come under any circumstance, consider compressor clutch bad.

Lets consider this route of power to check....

Battery +> Starter +> Bulkhead +> ACC Relay +> Fuse#10 +> Mode Switch +> Low and High pressure switches +> Bulkhead +> Compressor -> GND

Its probably a safe assumption that your getting power to the mode switch since your fan is engaging, so start from there.

[dmc6960]

Oh, and be sure you do these checks with the ACC on, but the engine OFF. You wouldn't want to manually trip the compressor with no charge in the system.

[Ron]

We know the mode switch is getting power because (I assume) the blower motor works, so:
Turn the air to max and see if you have power to either side of the low pressure switch.
If not, it's back to the mode switch itself...
If so, check the harness where it feeds the compressor clutch pigtail.
If the feed has power, the clutch is bad.
If not, you are low of refrigerant (jump switch momentarily to bypass) or have a break between the two.

EDIT: Check and see if there is ANY pressure (with the engine off ;-)

[Ron]

Before tackling the charge, lets check the electrical... .

I agree!!!

I was going to suggest jumping the compressor but wanted to know if it was empty for obvious reasons...


Meanwhile I was typing out a procedure to chase the power...BUT someone beat me to it :hihi2:

WTH!!! ---I thought I deleted the previous post (I did) and now I still cant even though it acts like it does. And I can't type past the smily w/o draging it behind something else first.
Wierd!...I'm going to log off/on.


...well that didn't work.
Still can't type past a smily w/o moving it first.

Anyway,

He said the compressor would not trip if the low pressure switch was jumped.
Oops I missed that....

[Ron]

Oh, and be sure you do these checks with the ACC on, but the engine OFF. You wouldn't want to manually trip the compressor with no charge in the system.
lol...reread all of this and bet you and I could make one hell of a soup...
:Headspin:

[David T]

All you need is a tire gauge to check the pressure on one of the service ports. If you do not see at least 60 psi (not running) the refrigerant has gone Bye Bye. If you don't even have a tire gauge just stick something pointy at the valve core for a second and see if there is any significant pressure. You can always rig up a wire from the battery post jumper directly to the compressor but you should not run it for any length of time without enough refrigerant. To jump the low and high pressure switches all you need are some bent up paperclips. If jumping the switches doesn't get you any power to the compressor you probably have some wires (3) in the wrong place on the Mode switch.
David Teitelbaum




I agree!!!

I was going to suggest jumping the compressor but wanted to know if it was empty for obvious reasons...


Meanwhile I was typing out a procedure to chase the power...BUT someone beat me to it :hihi2:

WTH!!! ---I thought I deleted the previous post (I did) and now I still cant even though it acts like it does. And I can't type past the smily w/o draging it behind something else first.
Wierd!...I'm going to log off/on.


...well that didn't work.
Still can't type past a smily w/o moving it first.

Anyway,

Oops I missed that....

[Ron]

+1

=======

We out number you dude...go do the tests already!

[ccurzio]

We out number you dude...go do the tests already!

I'm in no way refusing or arguing. I just won't be equipped to do most of them until this weekend. :)


All you need is a tire gauge to check the pressure on one of the service ports. If you do not see at least 60 psi (not running) the refrigerant has gone Bye Bye.

This, however, I can do immediately. Where can I find a service port?

EDIT: Nevermind, this was easy enough for me to figure out on my own. Unfortunately, while my tire gauge doesn't fit on these particular ports, I momentarily pushed in the needle. Surprisingly, there was a very forceful hiss. It would appear that I do indeed have refrigerant.

Again, this is unrelated to the actual problem with power to the compressor but it's a very good thing to know.

[stevedmc]

All you need is a tire gauge to check the pressure on one of the service ports. If you do not see at least 60 psi (not running) the refrigerant has gone Bye Bye. If you don't even have a tire gauge just stick something pointy at the valve core for a second and see if there is any significant pressure.

Won't this vent harmful gases into the atmosphere?

[ccurzio]

I just took a trip to Autozone and went ahead and bought a decent tire gauge. It may be the case that I actually don't have sufficient refrigerant since it only reads 30psi on the service ports.

[David T]

With only 30 PSI you definitely have a leak and have lost enough of your refrigerant that the low pressure switch will not allow the compressor to run. The good news is at least you haven't gotten to atmospheric so the system is probably not contaminated. I would not worry about any electrical problem till you find and fix the leaks and get the system refilled. If you have the original hoses they should be replaced along with the accumulator/dryer.
David Teitelbaum

[Ron]

I'm in no way refusing or arguing. :)

8) never thought that.

[nullset]

I can look at your A/C at Freeside on Saturday or Sunday. We can check the pressure, and vacuum/recharge if needed.

--buddy

[ccurzio]

I can look at your A/C at Freeside on Saturday or Sunday. We can check the pressure, and vacuum/recharge if needed.

--buddy

I'm going to be in Nashville until Monday, unfortunately.

Also, as far as I know I'm still on R12. Do you have R12 refrigerant?


If you have the original hoses they should be replaced along with the accumulator/dryer.

You wouldn't happen to know the part numbers for each of these, do you? I have the accumulator, I just need to know which hoses should be replaced as well.

Thanks.

[nullset]

I'm going to be in Nashville until Monday, unfortunately.

Also, as far as I know I'm still on R12. Do you have R12 refrigerant?


Yes, I have some R-12 I can sell you.

If you were passing through atlanta, I'd give you a canister to take up to Ron…… drat!

--buddy

[Ron]

Also, as far as I know I'm still on R12. Do you have R12 refrigerant?

:hysterical:...only God has more R12 than Buddy.

[nullset]

:hysterical:...only God has more R12 than Buddy.

Actually I think you have more than I do……

I'm not sure how much is in my machine right now, but my cars and cylinders are both empty. I now have 2 empty cylinders, and I think 7ish pounds of R-12. The machine can hold more, though….. Do you still have some surplus?

--buddy

[Ron]

Actually I think you have more than I do……
I'm not going to ask what your point is here...:deviltail:




I'm not sure how much is in my machine right now, but my cars and cylinders are both empty. I now have 2 empty cylinders, and I think 7ish pounds of R-12. The machine can hold more, though….. Do you still have some surplus?

--buddyYeah it's still complaining about being too full...

[ccurzio]

So I bypassed both the high pressure and low pressure switches and sent power straight through. Started the car and switched to MAX, and lo, the compressor is now getting power. So either one or both of the switches is bad, I'm low on refrigerant (which we know), or both.

Next steps: fill the damn thing with some refrigerant. Buddy, if you can set aside some cans of R12 for me I'd very much appreciate it. Second, I'd also like to have spare switches on hand just in case. Problem is, I can only locate the low pressure switch. Does anyone have a part number for the other one?

EDIT: Alrernatively, if anyone knows anywhere in the Nashville area I can get my hands on some R12 that'd also be great.

[David T]

To check the switches you can just use an ohmmeter. The high pressure switch should have continuity, the low pressure switch should not. Rare that a switch is actually bad, sounds like they are doing what they are supposed to. I caution against just topping off with more -12. You really should look for and fix the leaks. I would not trust the old hoses. I would replace them. In replacing them you eliminate them as a source for leaks and all of the seals associated with them. It is also a good time to check and change the oil. "Fixing" this by dumping in more -12 is not going to last long.
David Teitelbaum

[ccurzio]

In all honesty, topping it off is exactly what I am going to do. I fully plan on refurbing the system with new hoses and such, but only as part of a full-on R134A conversion. Any leaks I have at this point are certainly not bad enough to invalidate any interim fix efforts.

[DMCMW Dave]

Rare that a switch is actually bad, sounds like they are doing what they are supposed to. David Teitelbaum

In my experience the low pressure switches go bad all the time, but usually they still work - but leak.

[Ron]

Why not jump one pressure switch at a time at this point ?:confused0:?

[ccurzio]

Because I'd rather make sure they're good and are actually doing their job rather than trying to guess at whether they're failing or not.

If I can refill the system and determine they're working fine, that's cool with me. If I refill the system and determine they're still busted, I spend $8 or $16 (if someone can actually find me the high pressure switch part number) and then crank on I'm fine with that too. I just need a solution of some kind for the time being.

[jawn101]

This may be O/T but is there a documented procedure for testing the high and low side pressures with R134a? My system is fully converted with all new hoses and compressor etc, and is tight/not leaking - but I did have a leak when we first did the conversion. After tracing and fixing the leak, I put some more refrigerant into the system but feel like the cooling isn't what it should be. It is possible that between injecting dye and recharging that I went too far. I do own manifold gauges and a vacuum pump (pump shouldn't be needed to check the pressures) but am not sure what the procedure is and what pressures I should be seeing with the new refrigerant.

Do you just hook up the gauges to the service ports on the compressor, start the engine, put the A/C on max cooling and watch the gauges as the compressor cycles on and off?

[stevedmc]

This may be O/T but is there a documented procedure for testing the high and low side pressures with R134a? My system is fully converted with all new hoses and compressor etc, and is tight/not leaking - but I did have a leak when we first did the conversion. After tracing and fixing the leak, I put some more refrigerant into the system but feel like the cooling isn't what it should be. It is possible that between injecting dye and recharging that I went too far. I do own manifold gauges and a vacuum pump (pump shouldn't be needed to check the pressures) but am not sure what the procedure is and what pressures I should be seeing with the new refrigerant.

Do you just hook up the gauges to the service ports on the compressor, start the engine, put the A/C on max cooling and watch the gauges as the compressor cycles on and off?

The low side should read between 30 and 40 lbs when the compressor is engaged if using r134a.

[jawn101]

The low side should read between 30 and 40 lbs when the compressor is engaged if using r134a.

Thanks Steve. So my procedure sounds right? What should the high side read? Does it matter?

[stevedmc]

Thanks Steve. So my procedure sounds right? What should the high side read? Does it matter?

I believe the high and low side should read about the same (within 15 pounds of each other) when the compressor is not engaged. I normally don't mess with the high side though so I could be completely wrong. If memory serves me correct, mine is around 100 lbs when the compressor is not running.

Btw, the high side does matter. Both sides are supposed to be balanced when the compressor isn't running. If the pressures aren't close on both sides you've got something wrong.

[jawn101]

Got it, I'll check this out tomorrow after work. Thanks!

[David T]

In my experience working with older cars, when you "top off" and get a system that hasn't been running in a long time going again, it leaks a LOT faster and in many cases you wind up blowing hoses. I haven't seen any low pressure switches leaking but Dave S sees a lot more cars than I do. I can't argue with the logic of topping off and getting the system going to make sure it all works. All you are really risking is some -12. If the hoses don't blow you are way ahead! Just do a through leak check. Put some metal caps on the service valve ports when you are done and test them for leaks too. It is not very comfortable driving a Delorean without a well functioning A/C!!!!!!!!!!!!!
David Teitelbaum

[Ron]

Because I'd rather make sure they're good and are actually doing their job rather than trying to guess at whether they're failing or not.

You would have to force the compressor to run long enough to over-pressurize the system to know that...not a good idea.

What I was getting at is, if you jump the low pressure switch only and the clutch engages, you know the high switch IS doing its job (WRT the problem) -- If you jump the high switch only and the clutch engages, you know it IS failing.
Note:
The high switch passes current until there is a high pressure safety problem...no other function.
The low switch passes current whenever the charge is within a given range...low/high it shuts off.
(FWIW- They aren't know to be "flakey"...but often leaky.)

Solution "for time being"- If you take 515 on the way home from Nashville, you are ~35 minutes from here and I need to get some R12 out of my station (I junked two cars and now it is so full it refuses to evacuate).
PM me for phone-directions, I'll hook you up.

[David T]

You really do NOT want to overpressurize the system to "test" the high pressure switch. Too big a chance of REALLY blowing hoses! A simpler way is to just run the A/C and shut the fans off. That will cause the pressure to skyrocket but again, I would not do it as a test. All you really need to do is jump the low pressure switch momentarily. If the compressor and the cooling fans run you know the low pressure switch is holding back the compressor from running. All that is left is to confirm the low side pressure is too low.
David Teitelbaum

[stevedmc]

You really do NOT want to overpressurize the system to "test" the high pressure switch. Too big a chance of REALLY blowing hoses! A simpler way is to just run the A/C and shut the fans off. That will cause the pressure to skyrocket but again, I would not do it as a test. All you really need to do is jump the low pressure switch momentarily. If the compressor and the cooling fans run you know the low pressure switch is holding back the compressor from running. All that is left is to confirm the low side pressure is too low.
David Teitelbaum

I've never had to replace pressure switch, but I've got very little AC experience other than the Delorean and my Geo Metro. How expensive are these switches? Why not just replace both, flush the system with mineral spirits and an air compressor, put the thing back together, vacuum it, and fill with r134a?

Flushing the system with an air compressor does two things. It cleans out years of gunk and it also tells you if one of the lines is clogged or not.


Edit: I've never flushed an AC system. This is just my opinion.

[jawn101]

Got it, I'll check this out tomorrow after work. Thanks!

OK A/C experts, here are some readings I just took. Does this sound right?

All readings were taken at ambient temp, of about 82 F in the garage (shade)

Engine cold, not running: 60 PSI Low, 70 PSI High

Engine running at idle, compressor engaged, system at MAX A/C, vent flap to full cold, blower fan at 4: 38 PSI Low, 175 PSI High
Engine running at 1800 RPM, compressor engaged, system at MAX A/C, vent flap to full cold, blower fan at 4: 26 PSI Low, 220 PSI High

After 5 minutes doing various tests, the system was blowing about 45-48 degrees from the door vent holes in the dashboard, which is about
40 degrees colder than ambient. Spelled out like that it sounds pretty damn good I guess, but when it gets to be 110 ambient and the car is 175 inside 40 degrees won't feel like much of a difference.

Should I be expecting more from it or is this about normal? Some folks say they almost feel the need to wear a jacket in the car when the A/C is going, but I'm fat. Am I just expecting too much? :)

[Bitsyncmaster]

OK A/C experts, here are some readings I just took. Does this sound right?

All readings were taken at ambient temp, of about 82 F in the garage (shade)

Engine cold, not running: 60 PSI Low, 70 PSI High

Engine running at idle, compressor engaged, system at MAX A/C, vent flap to full cold, blower fan at 4: 38 PSI Low, 175 PSI High
Engine running at 1800 RPM, compressor engaged, system at MAX A/C, vent flap to full cold, blower fan at 4: 26 PSI Low, 220 PSI High

After 5 minutes doing various tests, the system was blowing about 45-48 degrees from the door vent holes in the dashboard, which is about
40 degrees colder than ambient. Spelled out like that it sounds pretty damn good I guess, but when it gets to be 110 ambient and the car is 175 inside 40 degrees won't feel like much of a difference.

Should I be expecting more from it or is this about normal? Some folks say they almost feel the need to wear a jacket in the car when the A/C is going, but I'm fat. Am I just expecting too much? :)

You can't get the air temp much colder and not ice up the evaporator. Then no air will flow through it. If you want more cooling, you need to move more air faster.

[jawn101]

You can't get the air temp much colder and not ice up the evaporator. Then no air will flow through it. If you want more cooling, you need to move more air faster.

Alright, so the refrigerant system is working like it should. I need to focus on other ways of using that chilled air to make the car cool like fixing the door vents, tinting the windows, getting my headliners replaced so it's not just bare stainless over my head, and losing 20 lbs :)

[David T]

Make sure the boot on the center vents is on right. Make sure the ducts in the doors are not leaking into the doors. Make sure the large hole under the dash all the way up and to the left over the dead pedal is sealed. Make sure the fan is turning in the correct direction and both cooling fans are pulling in air through the radiator from front to back. Check that the outside air flap is closed when in MAX. Pull the fan motor and make sure the evap coil is clean. Your readings sound good. The compressor should be cycling quickly at 1800 rpm. Make sure you do not freeze up your coil with 26 psi. Your high sides a little too high, probably because the car was not moving and you didn't have a fan in front of the car.
David Teitelbaum



Alright, so the refrigerant system is working like it should. I need to focus on other ways of using that chilled air to make the car cool like fixing the door vents, tinting the windows, getting my headliners replaced so it's not just bare stainless over my head, and losing 20 lbs :)

[jawn101]

Make sure the boot on the center vents is on right. Make sure the ducts in the doors are not leaking into the doors. Make sure the large hole under the dash all the way up and to the left over the dead pedal is sealed. Make sure the fan is turning in the correct direction and both cooling fans are pulling in air through the radiator from front to back. Check that the outside air flap is closed when in MAX. Pull the fan motor and make sure the evap coil is clean. Your readings sound good. The compressor should be cycling quickly at 1800 rpm. Make sure you do not freeze up your coil with 26 psi. Your high sides a little too high, probably because the car was not moving and you didn't have a fan in front of the car.
David Teitelbaum

Thanks David. I will check the hole in the footwell, and I know I need to slap some tape over the hole in the back of the heater box like I just suggested to another member in another thread. Center vent boots are great but the door vents need improvement and I have parts coming for that. The rad fans and AC fan are both working well and turning the correct direction. When I opened and re-closed my manifold gauges after disconnecting them I noticed the high side gauge was reading a bit above 0 even with nothing attached, so it must be off by about 5 PSI. How would I verify the air flap is closing in max? Is it visible somewhere?

The one thing that concerns me about your comment is that the compressor wasn't cycling at all in this scenario. It clicked on and I didn't notice it click off during the test, although I definitely feel/hear it turn on and off during normal driving.

[ccurzio]

Hey Ron, sorry I didn't get back to you today. Had a bit of an emergency when my car completely broke down on my way home from Nashville. So my priorities today were quickly shifted, and my DMC ended up being carried home on a flatbed.

[Ron]

I've never had to replace pressure switch, but I've got very little AC experience other than the Delorean and my Geo Metro. How expensive are these switches?
< $20.00, cheaper online.



Does this sound right?


I don't agree that your pressures are correct...
Mainly because the high and low side should be the same if it has been given a reasonable amount of time to equalize -- It would take two obstructions to give you a steady 10psi difference. That's extremely unlikely, and more so since it's basically working ok. Check you gauges!
Also, IF an R12 vehicle has been shut down overnight in an ambient temp of 82F and you check the pressures w/o ever starting the engine, both sides should read ~87.2F. [Ref- any AC Temp-Pressure conversion chart]

At 82F (an external box fan at radiator is req. if it's been on the road, idling long period, etc.), a R12 delorean system low side should be 29PSI (+/- 3) and the high 168PSI (+/- 22) -- Readings taken when clutch cycles off (if it does). Discharge should be 36F (+/- 2). [Ref- WS Manual N:09:01]
Note these values are for a new system.
Things aren't jiving, so again, check your gauge(s), else all of this means NOTHING!

+1 Dave M !!

+1 David T [I agree with your thinking (high-high => condenser hot...), but I'd almost bet his gauge is way off on the high side -- If it is off 5 when at the bottom of the gauge, and has a difference of +10 when it should be 60 (ie matching low side...~16%?), the numbers all make more sense, especially with poor transfer at the condensor...it may be a bit low! Agree?]

As for the performance you are expecting- A rule of thumb is that you can never expect more than 20F below ambient, BUT the "ambient" changes when you select MAX because you are cooling the same air over and over. So, I agree that your best bet is making the cabin air tight. (The cabin is relatively small for the system as it goes, but that's part of being out west I guess ;-) You should be able to get it "comfortable"...it just takes a while to transfer that 175-110=65 degrees worth of energy stored in all of that metal, plastic, etc., not to mention the air you start with and the sun beaming down all along....)
SOS - Make sure the ducts are clear and tight, the fan is good and the evaporator (and condenser) is CLEAN.




Hey Ron, sorry I didn't get back to you today. Had a bit of an emergency when my car completely broke down on my way home from Nashville. So my priorities today were quickly shifted, and my DMC ended up being carried home on a flatbed.
NP!
Ah hell! -- What happened??



The one thing that concerns me about your comment is that the compressor wasn't cycling at all in this scenario. It clicked on and I didn't notice it click off during the test, although I definitely feel/hear it turn on and off during normal driving.
There are scores of variables that affect the low pressure switch pressure, but as long as they don't push it out of its operating range, it will have no effect on the switch cycling the clutch. It's not all that uncommon to see this around 80F.

[jawn101]

I don't agree that your pressures are correct...
Mainly because the high and low side should be the same if it has been given a reasonable amount of time to equalize -- It would take two obstructions to give you a steady 10psi difference. That's extremely unlikely, and more so since it's basically working ok. Check you gauges!
Also, IF an R12 vehicle has been shut down overnight in an ambient temp of 82F and you check the pressures w/o ever starting the engine, both sides should read ~87.2F. [Ref- any AC Temp-Pressure conversion chart]

First, Ron - thanks!!

OK, when I get home tonight I will take the face off the high gauge and zero it, then do the tests again. For what it's worth, this is a fully converted R134a system - does that change any of your thinking here? I imagine the physics are the same but the pressure/temp comparison will be slightly different. Tell me more about the 'two obstructions' thought? I can't be the first person to work on this system, and while I did replace most of it I left the factory condensor and evaporator in place for financial/difficulty reasons (and because they didn't seem to have any problems) - so there could be a ghost in the machine.



At 82F (an external box fan at radiator is req. if it's been on the road, idling long period, etc.), a R12 delorean system low side should be 29PSI (+/- 3) and the high 168PSI (+/- 22) -- Readings taken when clutch cycles off (if it does). Discharge should be 36F (+/- 2). [Ref- WS Manual N:09:01]
Note these values are for a new system.
Things aren't jiving, so again, check your gauge(s), else all of this means NOTHING!


The car hadn't run in two days when I did this test, but I've never heard of the box fan trick before. I have one in the garage, should I set it up blowing into the radiator to simulate movement on the road?



As for the performance you are expecting- A rule of thumb is that you can never expect more than 20F below ambient, BUT the "ambient" changes when you select MAX because you are cooling the same air over and over. So, I agree that your best bet is making the cabin air tight. (The cabin is relatively small for the system as it goes, but that's part of being out west I guess ;-) You should be able to get it "comfortable"...it just takes a while to transfer that 175-110=65 degrees worth of energy stored in all of that metal, plastic, etc., not to mention the air you start with and the sun beaming down all along....)
SOS - Make sure the ducts are clear and tight, the fan is good and the evaporator (and condenser) is CLEAN.


Good point, I hadn't considered that re: recirculated air. I will definitely address all the other factors in the cabin to improve the performance as much as possible.



There are scores of variables that affect the low pressure switch pressure, but as long as they don't push it out of its operating range, it will have no effect on the switch cycling the clutch. It's not all that uncommon to see this around 80F.

Good to know, I won't worry about that then. I know it cycles, I've heard/felt/seen it do so, just not during this brief test.

Thanks again!

[Ron]

OK, when I get home tonight I will take the face off the high gauge and zero it, then do the tests again. For what it's worth, this is a fully converted R134a system - does that change any of your thinking here? I imagine the physics are the same but the pressure/temp comparison will be slightly different.
Not really. Pressures will be higher above ~70F (Another rule of thumb: 70F = ~70 psi for R12 and 134a...that is where they cross with 134a becoming the higher...check out the conversion chart (http://dmctalk.org/attachment.php?attachmentid=3771&d=1313473293), you'll see) The WS performance data chart will be off...forget it.
No external fan and/or 134a may be the cause of the high pressure David mentioned.
All mote until you can trust the gauges! ;-)



Tell me more about the 'two obstructions' thought?
Again, I doubt it is an issue here...
Anyway, the refrigerant is just going in a circle never being truly shut off. Very basically, you have a pump with the input and output connected together and a controlled leak via a fixed size tube from one into the other. If you get a blockage somewhere and shut it off, it will just balance out since it can flow the other way, so it will still equalize. (Running is a totally different situation...For example, say it has a blockage before the orifice. The compressor will try to pull everything after the blockage through the orifice and output it, driving the high side way up while the low side will go way down ("negative"). Where it is determines what burns up, freezes up, or blows up ;-)


The car hadn't run in two days when I did this test, but I've never heard of the box fan trick before. I have one in the garage, should I set it up blowing into the radiator to simulate movement on the road? You got the idea! (You have to be sure the fan puts out enough air...measure it in front of the radiator. And when you think everything is right, take it for a short cruse and check it right when you get back.)

[jawn101]

OK Ron - here's my update for today. I really think based on what I saw just now that I need to insulate the cabin, shut up and enjoy it.

Zeroed my gauges. The angle makes it look like the low side isn't quite but it was when viewed from dead on.
http://dmctalk.org/attachment.php?attachmentid=10022&d=1335912811

Here's the readings with a cold engine, not running. Ambient temp today was about 75 F. It's about 72 PSI on both sides, a little higher than yesterday but a lot more equalized.
http://dmctalk.org/attachment.php?attachmentid=10021&d=1335912811

Here's what I read with the engine at idle, MAX A/C, max cold, max fan. It's about 30 low, 150 high
http://dmctalk.org/attachment.php?attachmentid=10026&d=1335912848

Here's what I read with the engine at 1800 RPM, MAX A/C, max cold, max fan. About 20 low 175 high. That seems pretty low on the low side. I did have my box fan in front of the radiator today.
http://dmctalk.org/attachment.php?attachmentid=10025&d=1335912843

After a 5 minute trip to the gas station, here's what I was seeing (at idle, after I pulled in) - about 35 low 160 high
http://dmctalk.org/attachment.php?attachmentid=10023&d=1335912832

And a temp reading in the door vents at the gas station - 31.9 F??? It is hard to complain about that.
http://dmctalk.org/attachment.php?attachmentid=10024&d=1335912837


So aside from the fact that the low pressure seems to be getting pretty darn low, I don't think there's an issue here.

As a side question - taking all these readings leaves residual pressure in the manifold gauges when you disconnect them. Does that pose a risk of screwing up the pressure in the system? Or will it be OK if this isn't a daily activity.

[stevedmc]

31.9 degrees? What seems to be the problem? The title of this thread says something about a non functioning ac.

[jawn101]

31.9 degrees? What seems to be the problem? The title of this thread says something about a non functioning ac.

Yeah, obviously I don't fall into this category. I am curious if my pressure is too *low* now but I think it's just a hot cabin in the hot sun and not actually a problem.

[Ron]

As a side question - taking all these readings leaves residual pressure in the manifold gauges when you disconnect them. Does that pose a risk of screwing up the pressure in the system? Or will it be OK if this isn't a daily activity.Looks good to go...check your high side when it is real hot out tho... Don't worry about the tiny bit in the hoses.
GOOD JOB!

[ccurzio]

For the first time since owning my car, COLD air comes out of the vents when the air conditioner is on. :)

A huge thanks to Ron for helping me out yesterday. It was a long day of trying to locate any amount of R12 before giving up and saying "screw it" and just converting everything over to R134A. Ron says my system holds pressure extremely well and there doesn't appear to be any leaks.

The system isn't quite as cold as it should be (49-54 F), but cold air of any kind is a tremendous relief compared to not having any AC at all.

[David T]

When you first called out the pressures you neglected to mention you were on -134. These pressures are too low, both the high AND low sides. You need more refrigerant and you will have to adjust the low pressure switch so you cycle at the higher pressures.
David Teitelbaum





For the first time since owning my car, COLD air comes out of the vents when the air conditioner is on. :)

A huge thanks to Ron for helping me out yesterday. It was a long day of trying to locate any amount of R12 before giving up and saying "screw it" and just converting everything over to R134A. Ron says my system holds pressure extremely well and there doesn't appear to be any leaks.

The system isn't quite as cold as it should be (49-54 F), but cold air of any kind is a tremendous relief compared to not having any AC at all.

[jawn101]

Looks good to go...check your high side when it is real hot out tho... Don't worry about the tiny bit in the hoses.
GOOD JOB!

Thanks Ron. I hope the info we traded is helpful to another A/C novice like myself in the future!


It was a long day of trying to locate any amount of R12 before giving up and saying "screw it" and just converting everything over to R134A. Ron says my system holds pressure extremely well and there doesn't appear to be any leaks.


You just up and converted it in an afternoon? Awesome, those are the best kind of friends to have :)

[ccurzio]

When you first called out the pressures you neglected to mention you were on -134.

:confused0:

...because I wasn't on 134. Did you read my post? It was just converted over last night.

What pressures are you even talking about? The only time I ever mentioned anything about pressure was when I tire-gauged the service port and found 30 psi.

[jawn101]

:confused0:

...because I wasn't on 134. Did you read my post? It was just converted over last night.

What pressures are you even talking about? The only time I ever mentioned anything about pressure was when I tire-gauged the service port and found 30 psi.

Unless he meant to reply to me? I obviously had lots of detailed pressure readings but did say in a prior post that the whole system was 134, and Ron said the pressures looked good to him...

[David T]

Things can get confusing when I reply to one another responds. I was replying to the detailed pressure readings and I thought they were for an -12 system. If they were for a -134 system they were low and for a -12 system they were about right. Sorry if I added to the confusion. BTW I think it was the same system he said was not cycling. It MUST cycle or it will freeze up.
David Teitelbaum





Unless he meant to reply to me? I obviously had lots of detailed pressure readings but did say in a prior post that the whole system was 134, and Ron said the pressures looked good to him...

[jawn101]

Things can get confusing when I reply to one another responds. I was replying to the detailed pressure readings and I thought they were for an -12 system. If they were for a -134 system they were low and for a -12 system they were about right. Sorry if I added to the confusion. BTW I think it was the same system he said was not cycling. It MUST cycle or it will freeze up.
David Teitelbaum

Ah, OK. Yes, it's R134. The system does cycle but just didn't during that initial test. I see/hear/feel the compressor come on and off all the time. The low pressure switch is also a recalibrated one intended for R134 and was replaced during the system conversion. So you think the system is actually *low* on refrigerant, despite the temperatures I was seeing?

[Ron]

NP guys! YW!

==========

Yeah the thread did 'mingle' a bit LOL

==========

Chris, after sleeping on it (and thinking some more ;-), I want to remind you to clean the condenser ASAP (both sides high usually means overcharged (it's not even close), so maybe dirty condenser fins, fans or air flow...) This should cover the symptom(s), except possibly the old accumulator. So, if the compressor proves itself, you should install the new accumulator you have along with an orifice tube while you are in there. And, yes, tweak the low pressure switch, but wait until it is well above our ~70F out -- Not to say to push your luck with the high pressures in any way tho because you are too close to success with a gamble at little expense for parts to blow it now! LOL

I'm still wondering why is looked as if someone flushed the system well, installed a new compressor and one can of refrigerant but not a drop of oil -- weird!!!

[Ron]

So you think the system is actually *low* on refrigerant, despite the temperatures I was seeing?Um...how can I say this...

32F! -- DON'T F~[# WITH IT! :neener:

[Bitsyncmaster]

Um...how can I say this...

32F! -- DON'T F~[# WITH IT! :neener:


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