Replaced the compressor and accumulator on my 85 with an R4 compressor. The first problem I had was the connector on my 85 would not on the new compressor. I found the correct pig tail and wired it up. Knowing the compressor wouldn't kick on due to no coolant, I ran jumper from a 12v battery to cycle the compressor to add coolant. After more than enough coolant was present to run the compressor, jumpers were removed and the connector hooked up to the compressor. Nothing, Would not engage. Pressure was good and coolant level was good. One thing that popped in my mind first was I had a custom PROM installed, the guy that programmed it wanted to know what I had deleted from the engine, and the A/C, was on that list. Is the A/C compressor controlled by the ECM? I'm not very good at testing switches and what not but If someone could point out things I could check I'd greatly appreciate it. One thing I did try was unhooking the low pressure and high pressure switches and jumped with a paper clip, clutch did not engage compressor but blew the A/C fuse. Another note, when I slide the control to MAX or any A/C setting, it does cycle the cooling fan so the climate control panel is OK?

 

It may have something to do with you putting coolant in the AC system. Most would put coolant in the radiator and refrigerant in the AC system. Either that or all your fiddle fkn with jumpers blew something.

 

Thanks for that worthless response. About what I expected.

 

Glad to see you weren't disappointed.

 

I do believe the ECM will control the clutch engagement on the AC. At least I know their are setting in the dynamic EFI system I put on my 85 as I can adjust when it disengages under throttle. I can also turn the AC off completely. So making an assumption that is in the stock BIN as well but others may have to confirm.

Since you've gone away from stock it will be hard for others to help diagnose especially since it sounds like you have a non-stock style compressor in the vehicle (being R4 should have had the factory wiring as plug and play). The clutch will not engage if the pressure is to low or to high, that is for sure. If your pressures are correct and you wired things up correctly then I would suspect it was turned off in the tune as well. Not sure what mods the car has to necessitate a custom tune but if it's still running the stock drive-train it may be worth sourcing a used stock prom. May be worth grabbing a FSM as it will help you trace down wiring issues as well.

Not to question things but if you had to jump the switch to get the clutch to engage so you could charge the AC system does that mean vacuum was not pulled on it? If not, I HIGHLY suggest you do that or anything you do to fix this situation wont last long as you would have had moister in the lines. You can rent a vacuum pump and the gauges from most auto stores for free if you don't wish to buy them.