2000 Cadillac A/C

[Mikel]

Hello,
The AC in my 2000 Cadillac just stopped working. There is refrigerant in the system and the compressor is turning.

The low side reads 65PSI and the high side reads 110 PSI. Normally I would think it's low on refrigerant and add some, but doesn't the low side seem too high for this to be the case? Could this point towards a bad compressor?

Thanks.

[Cornbinder89]

Well, you didn't tell us what model Caddy, but just a guess, it sounds like a variable displacement compressor stuck in low.
That is the 1st thing I'd look for.

[Mikel]

Sorry, 2000 Cadillac Eldorado ETC.

Will do some research on variable displacement compressors. Thanks.

EDIT: Looking at the compressor pictures in Rockauto, the compressors listed only have a connector going into the clutch. They don't appear to have the valving/solenoid variable displacement compressors seem to have.

[Cornbinder89]

IIRC the oem V5 compressor was a variable displacement compressor. Used internal valving to move from high to low.
Many of the new variable compressors use an easier to reach valve and many are solenoid controlled.
Not seeing a "wire" doesn't mean it isn't variable.
If you can't get gaskets and don't feel comfortable tearing into it, could be compressor time.

[Tom Greenleaf]

IDK for sure Caddy's did some tricks.
Question 1. is what is your ambient temp in front of grille? Why needed that's what the system is dealing with those pressures wouldn't make cool air and doubt a liquid to evaporate?

Question 2. Take a "static pressure" with engine off and fully cooled down note area temp underhood.

If asking for cool and it's not very warm outside it isn't going to blow cool air very low normally.

Eldorado probably all Caddy's automatic temp control inside car isn't going to do extremes even if you want to,

[Mikel]

IIRC the oem V5 compressor was a variable displacement compressor. Used internal valving to move from high to low.
Many of the new variable compressors use an easier to reach valve and many are solenoid controlled.
Not seeing a "wire" doesn't mean it isn't variable.
If you can't get gaskets and don't feel comfortable tearing into it, could be compressor time.

Sounds like a fun compressor to examine, but since these are notoriously difficult to access and are not that expensive, it's probably better that I don't take any chances.
Thanks.

[Mikel]

IDK for sure Caddy's did some tricks.
Question 1. is what is your ambient temp in front of grille? Why needed that's what the system is dealing with those pressures wouldn't make cool air and doubt a liquid to evaporate?

Question 2. Take a "static pressure" with engine off and fully cooled down note area temp underhood.

If asking for cool and it's not very warm outside it isn't going to blow cool air very low normally.

Eldorado probably all Caddy's automatic temp control inside car isn't going to do extremes even if you want to,

When I checked it yesterday, static pressure was about 70 PSI in a warm engine compartment (ambient was mid to low 70s at the time). Both hoses were hot. Hard to tell if from radiant engine heat. I will get a cold reading in a couple of days when I get back to the car.

On the HVAC controller - It was 76 degrees yesterday and I was getting zero refrigeration. I will try engaging the defrost and see if that makes any difference.

Thanks.

[Tom Greenleaf]

70s for static with warm engine heat, hoses felt hot. Some don't like them but infrared touchless thermos would help. If damning this to a compressor know air temp coming in thru grille can use a wired household (hang sensor out a home window) can be real telling like if in sun over dark surface it's much hotter than you think.

I say it's very low on a charge but don't just go adding anything the way to know is measure what comes out or if impossible (costly equipment) then into a well held charge put in the exact amount.

About now I think it's a least almost empty it's got something to use a sniffer to find it.

They don't like wind (mine don't) nor other cleaners, dirty surfaces with other something used there.

I don't know these real well but if variable and appears engaged it's probably bad.

Some you can get at thru a wheel well some you can't?

Know that if static pressure is lower the temp in F. it's in trouble.

Look for oily spots it's 22ish years old many you can tell pushing a Shrader will show color.

A UV light would help too.

Strong guessing on my part it's low find the leak now.

Other issue this might not pump refrigerant disconnecting battery neg, wait a bit it shoud work again then quit again.

Tools for everything could do that with some scanners or pay just for the diagnosis if you want to do this for one time use it's too costly IMO.

Prep for needing a compressor the hoses as shown in your pic use two different O right seals one thicker older than this were OE different colors could be have to go to a GM dealer other makes did that if pic is correct?

Last one (retired a while now) was like that.

Up to you what pain tolerance you have to pay for some of this or bite it and send it out?

[Mikel]

Thanks Tom. I'll do some more digging.

[Cornbinder89]

Well 134a @ 70 deg is around 71 psi static. That doesn't mean the charge is correct or in correct, only that it could be.
If it is 70 psi after running and under hood temps, then I'd say it is low.
If it is 70 psi after sitting all night, it could be correctly charged.
Pressure and temp are always linked. use the pressure chart in the resources section to guide yourself.

[Tom Greenleaf]

Mikel: Find that chart and suggest printing it out. Temp measuring is key also test the device with another know it's right then you know the pressure inside what you are checking.

For some time high pressure ports are disappearing (bummer) if having a problem like a trusted touchless infrared (use two) also keep air out even hose if adding IMO should be purged just a spit.

I'll pull a full vacuum then add thru high side reading pressure on low till just positive pressure - there's zero air in system then.

Sign off says MetroWest Boston (no ocean moderation) inland here so it gets over 100F for real and most also below zero near every winter.

Machines don't like that A/C is complex really doesn't either. Things that seal anything (doesn't matter what) seals expand or contract not always do so well either don't work or leak.

Roads "heave" means lumpy bumps, paved old roads (area dates to 1600s so most paved crack the debris is nasty ruins vehicles if not careful at switch seasons for A/C bust headlights, windows and a condenser up front - learn to not follow to close to vehicles in front of you sometimes a surprise wild damage.

I almost can't check performance of A/C well my shop is heated but 40F can make plain hot only lasts so long with a running vehicle got to be fast for even a credible test/check if done fixing one,

[Mikel]

Static pressure today at 50 degrees was 55 PSI. The problem is that with the compressor engaged, NOTHING happened. No pressure differential, or change in temperature in any hoses.

Thanks.

[Tom Greenleaf]

Too cold to mess with now. If truly variable rate plus whacked climate controls (have many - hate it) it's not going to cool or try to.

Static pressure for 50F is fine IMO is warmer from some engine heat not much to bump up pressure if totally accurate observations,

[Mikel]

Yes, but a week ago it was 76 degrees, with zero cooling happening.
Thanks.

[Cornbinder89]

Temp/pressure chart here:
R-134a vs R12 Temp Pressure Chart - Automotive Air Conditioning Bulletin Board

[bbrickson]

I am not guessing on this, I know for sure the compressor is a fixed displacement and it is in need of replacement. When engaged if functioning properly it would quickly pull the low side down to 24 PSI and cycle off with that high side pressure.
Static pressure can only tell you if there is enough pressure to close the clutch cycling switch at about 24 PSI. If the system has 2 oz or 5 pounds in it the pressure will be the same when it is not running. If the vehicle has been sitting overnight and it is 70F it will have 70 PSI in it full or nearly empty.

[Tom Greenleaf]

Please quit it! CCOT system can't be 24 PSI or freeze up evaporator.

Welcome here for suggestions is all they are at least have some clue so I'll suggest something.

Learn what "Change of state" means the exception is water (H2O) expands when cold when frozen then shrinks again as it gets colder.

That's high school physics!

[bbrickson]

I was referring to the low pressure switch opening the contacts and shutting the compressor off. The specs on this are even lower than 24 PSI.

Change of state has nothing to do with it. As long as there is some liquid refrigerant in a container and the vehicles a/c system is a container, the pressure will be exactly the same if it is nearly full or nearly empty, the temperature is the only factor effecting pressure.

Did you take physics in High School?

[Tom Greenleaf]

I actually have a degree in Automotive Sciences!

Not the point now here to help not judge folks.
A very real point is whatever ports use the OE cap is the final seal are not all the same many missing if too long needs replacing if corroded just don't bust things attempting to,

[Mikel]

I have bought a compressor and once the weather gets warmer I will replace it. Hopefully the screen in the orifice will give me an idea of whether the condenser is full of junk.

Thanks.