Hi all - my 82 242's a/c stopped working yesterday. The car is powered by a Ford V8, but other than the compressor and some of the hose connections being different, it's basically the Volvo factory/dealer installed expansion valve a/c system.

It's been converted to 134A and has worked fine for 3 years since the conversion (worked fine on R12 before that for 7 years with the Ford motor).

Didn't exhibit any symptoms or noises. No blown fuses. It's just that now when I turn the a/c activation knob, it won't engage the clutch. I can hear the switch 'click' as if it's trying to send power somewhere. I've checked at the pressure switch - and that's not the issue. It's not sending any power to the pressure switch at all. I've jumpered power to the pressure switch, and when I do, the clutch engages and the cooling fans come on just as they're supposed to. So something is not allowing power to get to the pressure switch.

I'd appreciate any and all thoughts, as well as a short tutorial on how that rotary a/c on/off/temp. modulation switch actually works. I'm gonna have to trouble shoot the system and there's nothing in my crappy Volvo repair manuals about it. I'd guess that it somehow checks for the blower fan to be running, and perhaps checks for the engine to be running before it will send voltage to the pressure switch on the filter drier. If the pressure switch says it's ok, it sends voltage to the clutch engaging the compressor. I'm almost positive that when he converted the car he DID NOT wire the a/c up in a way so that it's operated by the Ford ecu and a/c relay. I do have that circuitry in the car, but I believe it's unused.

Thanks in advance - Michael