Year: 1988
Make: GMC
Model: Sierra
Engine Size: 5.7
I'm driving my father's truck (1988 GMC Sierra). He doesn't know if it's been converted to R134a. That seems like a good bet, since we're in CA, and he knows the A/C has been "serviced" -- so mechanics have probably raised the issue.
But the possibility remains the truck's still using R12, and I wouldn't want to guess wrong: there's no sticker indicating a re-fit, the valve port fittings look original, and they don't fit an R134a recharging/guage kit I bought.
1. Is it out of the question a mechanic converted the system to R134a but didn't change valve port fittings?
2. Is there a simple way to check if the system contains R12 or R134a? (By smell?)
3. At engine idle the compressor cycles on/off literally ever 1 second; does that make lack of refrigerant the likely problem?
Using new valve adapters, I was able to get a tentative pressure reading of 55/25 psi, depending on compressor activation. I'm not sure what to make of that.
As you can probably tell, this is my first time working on A/C.
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John U.
Paso Robles, CA
Edited: Sun July 11, 2010 at 11:56 PM by john_u
Refrigerant analyzed by a shop with the proper equipment will be able to tell what refrigerant is in the system or the purity of the refrigerant.
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Thanks -- this information might save a trip to the wrong garage. I guess I should call around and ask who has this kind of equipment.
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John U.
Paso Robles, CA
If it's been converted it should have Acme type fitting connectors.
R-12 used 1/4 flare, and 3/16 flare on the high side in 1988 GM.
Can you post or link photos of the connectors?
Edited: Mon July 12, 2010 at 9:18 AM by Cussboy
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