To make a very long story short, after copius amounts of research I converted my truck to an electric fan setup out of a Town Car. The idea was to wire the system with two relays, a 75 amp unit that controled the fan off a temperature switch, and a 30 amp that caused the 75 amp unit to connect when the A/C came on. Looked good in theory...had the right plan...installed it all exactly to the plan...and it turned out the 75 amp relay I ended up with was quirky and the 85/86 pins were opposite of a normal relay. I figured that out eventually, and everything works like a charm now, but before I did, I think I overpressured the A/C compressor by feeding power into it instead of getting trigger power for the 30 amp relay. I was in the cab when it went off. It sounded like something blew up, and there was refrigererant everywhere under the hood. I saw enough of what happened to know it came from somewhere on the top of the compresor. I couldn't see any visible damage, so I figured it blew a seal. After I bled off the rest of the pressure, I replaced all the seals, and found none to be damaged. But one other thing I did find was what apprears to be a pressure relief valve on the top of the compressor. It's actually on one of the hose assemblies and protudes from the bracket where the hose bolts on. So, two questions...first, is this really a pressure valve? And two, if it does release pressure, is there any permanent damage to it or the compressor? I can't find it documented anywhere in the reference material I have.
Yes, if you are describing it correctly it is a pressure relief valve. No,,you shouldn't cause any major damage just by over pressuring it.That is what it is for. There are many things that can cause a system to over pressurize,and if it weren't for the relief valve,,you would blow o-rings and seals,,to say the least. One thing I would mention though,,,if you see alot of oil residue,I would think of adding a couple of ounces to the system.
And the best part is they are near impossible to find without buying a new hose assembly. I think napa had them at one time, but that was 3 years ago. If it blw it did it's job and save the compressor.
Ok....so it sounds like this is a one-use only item and not availabe as a seperate part. And from what I can see, isn't availabe as part of a hose assembly. It acutally sits in a steel line that connects the hose to the compressor...it's not really part of either but rather a stand alone part. Numberdummy, any thoughts on this one?
Thanks Matt....I'm finding in some other forums that I might not need to replace the valve. The compressor itself is ok...I got that to fire by briefly bypassing the pressure switch. I have a couple of hours tomorrow morning before I have to catch a flight...I'm going to try to get the system vacuumed and see if it holds. If it does I'll recharge it and see what happens.
You should put on a high pressure cutout switch like the one in this link: AC - HIGH-PRESSURE CUT-OUT SWITCH KIT - JCWhitney Auto Parts . I've used them on every R12 to R134A conversion I've done and they work great. With one installed you never exceed safe pressure because it shuts down the compressor clutch.