Ron Dame Posted March 1, 2023 Report Posted March 1, 2023 I've just started working on my sometimes operating A/C, but am a bit befuddled by what should be a simple wiring system on my 1980 with the GM A6 compressor.. Like no High or Low cut out switches, and sometimes power to the compressor, other times, none. So where are the cut out switches, relays, and assorted components so that I can isolate my problem?
Jim78 Posted March 2, 2023 Report Posted March 2, 2023 As you note, there is no binary pressure switch in the system. I added one in my system when I changed the compressor. The brown wire is direct from the thermostatic switch to the compressor clutch. The power to that switch comes via the black jumper from the fan switch. The yellow is the 12V supply to the fan switch. The black wire goes to the fan. The fan must be on for the clutch to engage. No relays. If the power is intermittent, there is probably an issue with one of the switches, or it's just the thermostat operating. A 12V test light would be an easy way to troubleshoot. Also, make sure that someone hasn't mixed up the wire locations on the switches. BTW if you ever need to replace your compressor, I highly recommend an aluminum replacement for the A6. Dimensionally identical, bolts right in, more efficient and about 20 lb. lighter!
Ron Dame Posted March 2, 2023 Author Report Posted March 2, 2023 I'm glad it is a simple as it looks, and no relay! Maybe today I can get it running enough to put the gauges on and see how much charge there is. There's something in the sight glass anyway.
pantera928 Posted March 2, 2023 Report Posted March 2, 2023 As Jim78 said, the aluminum A6 replacement does bolt right in. I am running it on my 1980
Ron Dame Posted March 3, 2023 Author Report Posted March 3, 2023 And an aluminum A6 is 134A compatible I assume?
Jim78 Posted March 3, 2023 Report Posted March 3, 2023 54 minutes ago, Ron Dame said: And an aluminum A6 is 134A compatible I assume? Yes. I'm running 134A in my '78.
pantera928 Posted March 3, 2023 Report Posted March 3, 2023 2 hours ago, Jim78 said: Yes. I'm running 134A in my '78. Me too
Ron Dame Posted March 3, 2023 Author Report Posted March 3, 2023 Great! what about the condensor? Did it need to be changed?
pantera928 Posted March 3, 2023 Report Posted March 3, 2023 1 hour ago, Ron Dame said: Great! what about the condensor? Did it need to be changed? I am running the original condenser. Some newer ones might be more efficient though. I replaced hoses and the receiver dryer
Ron Dame Posted March 6, 2023 Author Report Posted March 6, 2023 I fixed the fan switch and now the compressor runs as intended. Today we got to the low 70's so it was time to check pressures. Please note, I don't know much from a practical aspect of A/C systems. The system is still R12 and at 1500 RPM showed about 4 on the low side and 145 on the high, so it's clear I am undercharged. Outlet temp was actually higher that ambient temp, maybe 80F or so. I've got dye in the system, and so far find no leaks. I don't know when it was last serviced. I'll look again tomorrow. ASSuming I find no leaks tomorrow, is the leak so small as to be negligable, and so what do I do? The professional/legal reason is to change compressor oil and recharge with 134A, or change the compressor (A6) and recharge, replacing the drier/accumulator of course. Maybe hoses too. Or in a less legal/professional manner, can I top it off, and with what? PS, I will crosspost this on other sites so I get as many good and bad suggestions as possible!
pantera928 Posted March 9, 2023 Report Posted March 9, 2023 You may have an expansion valve stuck closed. I try to achieve around 30 PSIG on the low side and 2.5 times the ambient temperature in degrees F on the high side so if it was was 70 degrees F, then 2.5 times 70 would be 175 PSIG. You are obviously a little low but even with those pressures, you should see some cooling.
Gunslinger Posted March 10, 2023 Report Posted March 10, 2023 If the expansion valve is stuck…it needs replacement or the high side hose can literally explode ooff the compressor making a mess under the hood. Don’t ask how I know that. BTDT
Ron Dame Posted March 10, 2023 Author Report Posted March 10, 2023 15 hours ago, pantera928 said: You may have an expansion valve stuck closed. I try to achieve around 30 PSIG on the low side and 2.5 times the ambient temperature in degrees F on the high side so if it was was 70 degrees F, then 2.5 times 70 would be 175 PSIG. You are obviously a little low but even with those pressures, you should see some cooling. It must be stuck then, as it has no cooling at all. Guess it's time for a 134A changeover.
Ron Dame Posted March 13, 2023 Author Report Posted March 13, 2023 I thought I'd start pulling the trim panel to get to the expansion valve better while waiting to get the R12 evacuated. ... Now I have a new snag. Where I suspected I had screws holding the panel in, it seems more like a glob of metal, almost like it is soldered in place, which is justn plain silly. Nonetheless, What kind of fasteners hold the panels in, and how do I remove them ( 1980)?
Ron Dame Posted March 16, 2023 Author Report Posted March 16, 2023 Bump: How do I get the panels off of either side of the evaporator?
Jim78 Posted March 17, 2023 Report Posted March 17, 2023 22 hours ago, Ron Dame said: Bump: How do I get the panels off of either side of the evaporator? IIRC, there are screws buried in the carpet. Not easy to find.
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