Is my a/c compressor shot?

[Anduril]

The a/c on my wife's 1999 Cavalier no longer blows cold. This started back in January (yes some of us use our a/c in January...) when it was blowing cold until it suddenly cut off on the freeway. Went from blowing cold to warm just like that; I was in the car when it happened and it seemed like the compressor shut off. It would not come back on until we parked and went inside somewhere for a bit and came back out. I verified that the compressor was turning, but there was no cold air.

My immediate thought was that it was low on freon. I bought one of those recharge kits with the low-side gauge and hooked it up. The pressure on the low side was reading high with the compressor on or off, the system would not charge, and still no cold air.

We left it alone with non-working a/c until now. I finally bought a proper gauge set and these are the readings:

Compressor off: ~70-80 on both low and high side
Compressor on: Low side drops to ~65 and high side slightly over 80
Compressor on/engine revved: Low side ~50, high side ~100

The air gets *slightly* cool when you rev the engine, but not cold. Condenser stays cool to the touch. The compressor clutch engages, compressor runs and changes the pressure slightly, and the radiator fan runs.

A few other things to note: For the past year or so, the air out of the a/c has not been particularly cool at idle, but when the engine is revved/car is moving, it has cooled down to acceptable levels. The compressor makes a noise that's best described as being somewhere between a knock and a rattle at idle (I can't hear it at higher RPMs but maybe the engine just drowns it out) but it did that while the a/c was working too.

My best guess from all of this is that the compressor is simply worn out, and can no longer generate enough compression to effectively cool. Why it would just cut out all the sudden though, I have no idea.

Please, someone tell me I'm wrong here before I go spend money replacing it.

 

[Donald]

I think you should bring it some place. You need more equipment than just a set of manifold gauges. Vacuum pump, leak detector.

 

[Thax]

Sounds bad too me. Low side is a bit high while the high is too low. Sounds like it is time for a new compressor and drier.

 

[AdRock]

If that compressor was making knocking and rattling noises before it just quit there's a good chance the system is full of pieces of the compressor that have broken off etc. and that's why it won't pump.

So just from the info here I'd take all the connections loose, remove the orifice tube, and blow out all the lines. Then put in a new compressor, orifice tube, and drier.

 

[zzyzzx]

I also suspect that you have a bad compressor. Replace it or bypass it before it leaves you stranded. Yes, I have seen that happen at a friends house (compressor AND clutch locked up).

 

[Anduril]

For anyone interested, I finally completed repairs after about 3 weeks of procrastinating with the car sitting in the garage in various stages of being taken apart

Replaced compressor, orifice tube, and receiver/drier. The orifice tube was clogged with black carp (I don't know if this was part of the problem or not, but the kit I purchased came with a new one so I changed it). Flushed system, replaced o-rings, vacuum pumped, vacuum pumped again because I didn't know how to work my gauges and let air back into the system, and charged with 134a. A/C blows cold again, even at idle where it seemed to struggle before.

Only thing left to do is finish putting the car back together.

Total spent was $170 in parts and probably $200 or so in tools and equipment. Would have been more but I was able to loan the flush gun from Autozone. They had the vacuum pump too, but I already bought one before I even knew they offered loaner tools. At least now I have everything I need to do the a/c on my own car, which I will need to do soon (has a leak; I recharged it and it's gotten warm again after a few weeks).

 

[artificialist]

Black stuff clogging the orfice tube usually happens when the A/C fails. That is wear material from the compressor.

 

[zzyzzx]

Originally Posted By: Anduril
For anyone interested, I finally completed repairs after about 3 weeks of procrastinating with the car sitting in the garage in various stages of being taken apart

Replaced compressor, orifice tube, and receiver/drier. The orifice tube was clogged with black carp (I don't know if this was part of the problem or not, but the kit I purchased came with a new one so I changed it). Flushed system, replaced o-rings, vacuum pumped, vacuum pumped again because I didn't know how to work my gauges and let air back into the system, and charged with 134a. A/C blows cold again, even at idle where it seemed to struggle before.

Only thing left to do is finish putting the car back together.

Total spent was $170 in parts and probably $200 or so in tools and equipment. Would have been more but I was able to loan the flush gun from Autozone. They had the vacuum pump too, but I already bought one before I even knew they offered loaner tools. At least now I have everything I need to do the a/c on my own car, which I will need to do soon (has a leak; I recharged it and it's gotten warm again after a few weeks).


Obligatory:

 

[Anduril]

And none too soon, too!

 

[Chris142]

If you did not replace the condenser the repair may not last