I'm sure that by September you guys are all sick of AC problems, but I'll ask anyway. For the first time in the ten years I've owned my 94 Z28, the AC does not blow cold air. I bought the Harbor freight gauges, can tap and some freon. I hooked it all up, started the car and AC. The low gauge read 20 PSI to start, and crept up to 25 quickly, but I'm quite sure the compressor was not spinning. (The plate in front of the pulley should spin, right? I also did not hear the engine take the load.) I've read you can jumper the low-pressure switch to start the compressor and add freon, but most describe two wire sensors. The sensor I found on my 94 LT1 had a sensor on the same line, between the low-pressure quick-connect and firewall. But it has three terminals. I did not want to fry anything, so I did not guess. I think the wires were red, black and grey? I know you can hot-wire the compressor too, but it's buried pretty deep and looks to be a PITA to get to. Any ideas on the 3-wire sensor jump?

I hope someone can talk me thru this one. I did just fix my driver window motor, but that doesn't help much when it's 95° out.

 

It's a 5 volt reference sensor- it has 5 volt power, ground, and a signal wire to the pcm.

It is a real sensor, not a switch, it changes resistance so jumping the terminals probably won't work. But for reference, grey should be positive, red/black should be signal, and black should be ground (always check w/ a meter first, wiring diagrams aren't always correct).

Keep in mind that there is an a/c clutch relay in the electrical box under the hood that is very easy to get to, so I wouldn't bother with anything else. Just jump the two large terminals and add your refrigerant.

 

Thanks GreenDemon. I did try once before reading your reply. You are right, it made no difference jumping the three wire sensor grey to red. I did find the AC relay in the under-hood fuse box. But I was not sure what to jump there. I'll look for the two large connectors. Is there a way to test this relay? Is a jumper wire between the two largest sockets going to activate the clutch? Thanks again.

 

When my a/c quit due to low refrigerant I just pulled the PCM fuse for a few seconds to reset it. Then the a/c clutch engaged long enough to add the refrigerant.

 

You're correct, remove the relay, the two large terminals should be bridged, they are the switch part of the relay. Don't use a really tiny wire or you'll burn it up- 12/14 gauge would be best. It would be best to do this with your a/c gauge hooked up to the high side to keep an eye on things. Obiously you'll have to leave the low side not hooked up so you can add refrigerant.

Chances are it will leak back out sooner or later but if your can has dye in it you may be able to find it. Usually it's either a condenser or compressor.