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Will Pressure Release Valve Reset?

jackhild on Wed April 14, 2010 6:05 PM User is offline

Year: 1990
Make: Mazda
Model: RX7
Engine Size: 1.3
Refrigerant Type: R12
Pressure Low: 0
Pressure High: 0

The system is R12 and completely original, except the cooling fan. It has functioned flawlessly for the last 4 years. Then the fuse blew on my cooling fan. Wife was driving and didn't notice temps rising and the sound/feel of the A/C loading up until it was too late (note to self: it is not the Wifes fault, it is NOT the Wifes fault, it is not the Wifes fault...).

The system was close to zero pressure when she got it back to me. I assume the pressure release valve vomited my 28oz of R12 into the environment. I added just enough gas to bring pressure up, used my sniffer to check around and didn't find any leaks. So I charged about 1/3 of the charge. The system worked right, clutch cycling a little to quickly due to the low charge. I sniffed it again. Since I didn't find any leaks, I charged till the glass was *nearly* clear. Center vent temps on high recirc hit 39*. I drove the car around a little, then parked it for the night.

Next day, system was empty (5 psi at 80*) again.

Should the pressure release valve reset? Is the pressure release valve leaking? I cannot sniff anything there. (mac tools sniffer works pretty well) Is it possible that the compressor shaft seal has 'blown'? I can't sniff anything around there either.

Suggestions?

Thanks

Jack

jackhild on Wed April 14, 2010 7:02 PM User is offline

Never mind. I found a 'leak' in the center of the plug on the receiver/dryer. Looks like this is a pressure relief device. Can it be replaced or do I need a new dryer?

Thanks

Chick on Wed April 14, 2010 8:56 PM User is offlineView users profile

Some reset, others don't, if the new drier comes with the pressure relief valve, change it, if not you may need to change the pressure relief valve to be safe...

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

jackhild on Wed April 14, 2010 9:58 PM User is offline

Thanks Chick for the quick reply-


looks like it doesn't reset, it is some kind of fuseable material, probably melts at 200* or so.

Cussboy on Thu April 15, 2010 3:24 PM User is offline

Quote
Originally posted by: jackhild
Never mind. I found a 'leak' in the center of the plug on the receiver/dryer. Looks like this is a pressure relief device. Can it be replaced or do I need a new dryer? Thanks

Let me field this one, as I have some hands-on experience with the "heat fuse". I have a 1988 Mazda B2200 truck; my AC was originally Sanden SD 708 Model 7209 but compressor made noise when I bought it in 1994. I upgraded to a Sanden SD 708 Model 7225 which was the same compressor but had the high pressure release valve in its backside. Anyway, a few years later, waiting at a 2-minute traffic light one typical 116F summer day in Arizona, the heat fuse in the receiver-drier blew/broke, and my R-12 leaked out. Apparently this is the way Mazda protected the system back then, but I found out that heat fuse is not needed with the compressors that have the high pressure blow-out valve on them.

Anyway, it sounds like even though your compressor has that high pressure release valve, your receiver-drier still had the heat fuse. OK, here's the solutions: (1) replace the receiver-drier with a new one (make sure it has a plug there) or (2) simply screw in a metal pipe plug instead of the heat fuse. The kicker: the thread size of the plug I used is 1/16 inch NPT, so that won't be that easy to find, you may need to order on-line.

I have changed my receiver-drier since then with a more-recent compressor change, can't remember if the new receiver-drier came with a plug or I had to swap mine over. And, yes, my high-pressure release valve on the compressor also did seal by itself.

Edited: Thu April 15, 2010 at 3:29 PM by Cussboy

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