2002 Golf - A/C compressor pressure relief valve???

[Shenandoah]

Folks,

Oldest daughter was home over the weekend and said the A/C was cool but not cold. Connected the gauge set and the low side was reading low so I added some R134a. Got in the car and the vent temperatures were good. I pressed the accelerator and heard a "hiss" and a cloud of vapor for a couple of seconds on the drivers side of the car, then it stopped. Strange........Connected the gauge set back up and again, the low side was back to where it was when I first checked it. Added some more R134a to bring it back up and the same thing happened again when I hit the accelerator. Didn't have anyone around to help, so I really couldn't see where it was blowing off from?

Does the compressor have a pressure relief valve? I'm thinking the compressor might be on it's way out? Thanks.

Eric

 

[Genesis]

It does, but the RCV is supposed to control that. It sounds like its hosed.

 

[Fahrvegnugen]

Mines hosed up too. Planning to crawl under and open up the compressor and replace the rcv and see if that helps. $30 and and see if refrigerant works before replacing the compressor & drier. Seems the rcv is a $30 game of spin the bottle.

 

[Genesis]

Yep.

If its doesn't have gunk in it then it'll probably work. If it DOES then as soon as you replace it you'll blow all that "stuff" through the entire system and now you get to do the whole job anyway. But for $30, why not try it?

 

[turbocharged798]

What was the pressure on the high side?

 

[dieseldonato]

I just replaced the rcv valve in my 01, if it helps before I replaced the valve it didn't make cold and had little pressure differential across the low and high side. Like 80 and 110psi, throttle application didn't seem to change the pressures much. After I put a new rcv in I had 40 low and 180psi high side, and it remained pretty consistent with rpm changes. There is a pressure relief valve on the compressor head, although I have no idea what pressure it pops off at, I'd imagine it's pretty high.

 

[Genesis]

It is, and if it opens it will probably not seal again -- its there as a last-ditch attempt to prevent a ka-boom.

 

[Shenandoah]

Folks,

Still working on this problem.....Swapped compressors (from a good parts car I had) but compressor clutch won't engage or the fans turn on. Checked the fans through the thermo sensor connector on the radiator and they work fine. Going to jumper 12v to the compressor clutch to see if it engages. If it does, I'll take a look at the high pressure switch up by the firewall and the Fan Control Module under the front, driver's side frame rail.

Scanned with VCDS - no fault codes showing.

Eric

 

[dieseldonato]

I thought I had a clutch issue, but I didn't have the connector clipped together firmly. Stupid moment on my part. You can check with a multimeter to confirm you have 12v at the plug and ground at the plug to the compressor. It had a hot and ground making it easy to test both at once.

 

[KLXD]

I had the impression the relief on the pump was an all or nothing affair that did't reseat. Guess I was wrong

 

[Shenandoah]

Ok....an update. Drove up the hill to where my four VW mk4 parts cars are in the Golf with the AC on and the fan on 4. No AC. Left the car running while I'm getting ready to take the Fan Control Module off the "parts car Golf" when I hear the compressor kick on. I check the fans and they are now running and the AC clutch is engaged and turning. AC is blowing cold air.......

One strange thing with this Golf is the temp gauge will peg and the red coolant light on the dash will come on randomly. It is not overheating or low on coolant. It's always done that and after awhile it stops and the temp gauge reads normal. I've replaced the coolant temp sensor many times, still have the same problem with the temp gauge.

When I heard the compressor engage, I was standing there looking at the fans and the compressor. After a couple of minutes, they started to slow and almost stop. I looked at the instrument cluster and sure enough the temperature gauge was pegged and the coolant light was flashing. They then went back to normal and the fans and AC clutch engaged.

Looks like there is an electrical problem with the cluster? Unless there is some other sensor that controls the coolant temp gauge and the coolant light on the dash? Maybe the thermo sensor in the radiator above the Fan Control Module?

Eric

 

[jayb79]

coolant migration thru the level sensor maybe? This was an issue with some Mk4s.

 

[Shenandoah]

Jayb79,

Oh man, I never thought of coolant migration as the problem, but maybe it is. If so.......ugh.....

Eric

 

[Shenandoah]

Folks,

Just following up: The 2002 Golf has the immobilizer disabled. I put a different cluster in from one of my parts cars and ........ the A/C works just fine. Fans spin, A/C compressor clutch engages, cold air blows out of the vents. I'm not sure what the problem is with the original cluster? The temp gauge works fine in the replacement cluster. Maybe the circuit board or solder joints are failing on the original cluster? It does have 297k on it, but that's not too bad. The 2005 Jetta wagon has 443k.....

Eric