Another pothole on the long road back for my son's 1984 GLT. I was surprised that after evacuating the system and recharging with R12A (from Envirosafe), it actually blew cold (by 240 standards) air and held a charge. Yay! But then one day it just wouldnt' turn on. I checked for voltage at the pressure switch on the drier, and found none. Tried "hotwiring" it from there and the clutch engages just fine. The fuse is fine, so the problem obviously lies somewhere between the fusebox and the pressure switch. The schematic shows a delay relay and the thermostat/switch as the only parts in between (though of course in a 28 year old car, who knows where there might be an open....) I have no idea where the delay relay lives, and replacing the switch looks like a PITA. So....

I'm thinking of just hot-wiring the compressor clutch directly. Put in a relay, a switch on the dash wired to a source that's hot only when the car is running, and feed power to the pressure switch. Definitely ghetto, but he's a college student with no dough.

As I understand it, the problem with this is that the evaporator could freeze up and block air going through it, resulting in no cold air. Solution would seem to be manually switching off the compressor every so often. But is this REALLY an issue? Isn't it the same as leaving the thermostat switch in the orange range? Volvo says not to do that, but I never noticed a problem doing that on my '90. Seems to me that the A/C is so underpowered in these cars that I can't imagine the evaporator really freezing up. Plus, we live in Denver where the air is so dry that there's not much to freeze if it did get that cold. (Granted, might be a different story in the winter if being used for defrosting....)

So, am I overlooking something, or could this be a cheap/easy, albeit inelegant, solution?

You can do away with the delay relay by using a jumper wire in the socket. I did not know the 84 came with a delay relay?

The relay on my 86 resides on the right side of the console under the right lower panel. Mine failed and it is gone like a wayward cowboy!

You need to keep the thermostat control since this car is different than the 90 because it uses a low pressure switch to watch for flood back to the compressor.

A wire may have come off it so you may want to check it out!

Phil

Yes, the '84 does have the delay relay. You were dead-on in your diagnosis; after I tore into the dashboard further I discovered that one of the green wires to the thermostat had become disconnected. Frustrating that I hadn't found this BEFORE our current heat spell, but it's always nice to have a no-cost fix!

Anyone else chasing A/C wiring problems might find this site useful--I know that I did:

http://cleanflametrap.com/ac.html

Thanks!