Air Conditioning Compressor High pressure relief valve BLEW!!!!

[huntersirg]

Alright So I was starting to enjoy this car again for a few days after finally getting my a/c working, which is imperative during summer in Florida.....

Took forever to figure out why my compressor wouldn't kick on. Ended up being the relay and a break in the green compressor wire. Once this was fixed it kicked on and we had cold air and I praised the gods!!! Checked the low side pressure and it was at about 30 and about 90f out. I added one small can of r134a no stop leak junk which got it up top 40 and blowing super cold.

But.....Today it all went to hell! I was working on wiring the stereo, running the a/c and hiding from the mega mosquitoes we have here now for maybe 15-20min. Cooling Fan was running on high car wasn't overheating or anything and I get the dreaded PSSSSSST of my r134 getting blasted into the atmosphere. Shut the car off right away and checked the low side again it was up to 60psi. I let it all cool off for maybe 15 min. went back out and started her up again with the a/c off and in maybe 2 min. the valve blew again shorter this time.

I'm thinking maybe the orifice tube is clogged, but Im not sure if that would cause it to blow the valve. Anyone know anything about this valve (ie if it need to be reset)? I know I need a set of real gauges....

I've read all the threads I could find and so many are wrought with dead ends and no fixes found. PLEASE HELP me not make this another dead end a/c thread!

[huntersirg]

Before anyone goes and looks I couldn't find anything in the Bentley on the valve beside that it exists and is used for "servicing"

This my have happened because only one of the fans was working and the car wasn't moving, I really want to know if the valve blowing off like that has ruined anything???

[Seerlah]

What valve are you referring to? And where is it located?

[huntersirg]

I haven't had a chance to locate the valve on my car, from what I've gathered its on the compressor but I can seem to find anything in the Bentley or online as to it's specifics.

Here' a pic from another thread where it was leaking oil

[Seerlah]

Not quite sure, but looks like an oil drain. Wish I didn't throw my old compressor out. I would have dismantled it to be certain. On my car, there is no red cap. But it looks like a fitting held in place by the snap ring with a slot (under the red cap) that you place a flat head screwdriver to open the drain. This is from a quick look with a quick conjecture. Just taking a guess here. Orientation of where this sits when the compressor installed supports my guess. But still, it is just that.

There are no refrigerant vents on AC systems, only on cylinders (rupture disc).

[huntersirg]

Just went out to check a few things and even with the a/c off the compressor was running (explains why it blew the second time), I pulled the 267 relay which I'm sure is the a/c relay and it still was running, didn't want it to blow again so I just unplugged the compressors green connector by the PS res. which did shut it off thankfully. I though without that relay the clutch should not kick in???? Thinking that the high/low pressure wswich is bad as it didn't stop the compressor from building up to much pressure. Any thoughts out there?

[Seerlah]

High pressure switch is on your high pressure side and not your low pressure side. It is a fail safe for your head pressure, not suction pressure. With the 2 lines for your AC system on the right side of your engine bay (left, when looking from front), the HP switch is connected to the smaller line that the R-134 cans picked up at auto parts stores can not hook up to (on your condenser which is part of the high pressure side). Like you stated, you need a quality manifold gauge to at least see both your low and high pressure readings.

With R134A, you want the pressure around 35psig on the low suction side for a 40* evaporator coil. The high pressure side should have a pressure reading of 20-30*F above ambient temp going by the pressure/temperature chart.



And you are positive your climate control was completely off? Sorry, but had to ask.

[huntersirg]

Getting gauges tomorrow before I let it run at all. Yes everything was off but I was wrong the 370 is the a/c clutch relay. With the cover off the relay you can see it engages once its plugged in then when starting it dis-engages then re-engages after starting the engine. I can lift the contact on the relay up to turn off the compressor but it pops back down instantly this is with the a/c control panel off and dark no buttons stuck.

Must be a separate issue or could it be that the relay is faulty or whatever sends the single to the relay is faulty and caused the compressor to over pressurize the system and blow its load of r134?

Sucks going from so happy again with this car, right back to hating it!

[Seerlah]

I am going to say you know how a relay works. I don't know schematics for this vehicle, but am going to guess that the coil on it has a completed circuit from the climate control. Unhook it and hook it up to see if that alone will cycle the compressor. Well, that is what I would do. That would at least tell me that if it is a faulty signal to the relay telling the compressor to turn on and then diagnose from there. But if it changes nothing, at least that is one variable out the way.

[huntersirg]

Alright got the gauges and a new load reduction relay (370). The relay is not why the compressor clutch is getting power when the a/c is switched off. But it was only $25 and I've heard of them failing. It's on no matter what but there is a change in rpm when the a/c is switched on but the clutch remains engaged until I unplug the green connector for the clutch wire under the plastic power steering cover.

Now the aux fan isn't coming on and I still need to wire up the EFK (electric fan) I installed. So now I need to first see if the aux fan is getting power. Because the fans were not running the high side jumped up to 200psi and started climbing with the condenser getting hot. Low side was right a 35.

Maybe this is a intermittent fan problem which caused the high side to skyrocket and blow the relief! Still don't know where to start with the compressor stuck on?

For who ever can help me solve this I will send you some free Audi decals in what ever color you want!