mvvette97

Ok guys I just got the engine in my 94 and I also had to put a new compressor on since it was bad. It's not charged up or anything but I was thinking I would test the pump just to make sure the clutch worked. On older cars I just unplugged the pressure switch and jumped the wires over and the compressor would click or lock. I tried this on this car and I couldn't get it to do anything. i then ran a jumper down to the compressor and got it to work. But why can't I just jump it from the pressure switch like on older cars? Does the pcm have to allow power to the pressure switch? I even had the car running and the AC turned on. I took a test light and found one of the wires had power but it seemed low because the tester was dim. I was thinking there was a problem so I done the same test and checked for power on my 2000 trans am and it just barley lit the test light also and everything works fine on it. How the hell does this AC system work on these cars?

bobdec

On these cars it's not a switch it's a sensor. One wire (gray) is +5v reference , one wire (Black) is ground, and the third (Red/Black) is a sensor voltage to the PCM. Jumping any of them together can throw an A/C DTC code and may hold off normal operation till code/or PCM is reset. The PCM verifies pressure (refrigerant in system) and picks a relay in the under hood relay/fuse panel when the a/c switch is turned on. To force the A/C clutch on you have to jumper a bypass in the relay panel. Here's the schematic ref shoebox.. http://shbox.com/1/hvac_compressor_control.jpg Pull the relay & jumper pins B1 (+12V ign voltage) from fuse to pin B4 (clutch pick). NOTE..it will spark and this is a test only procedure.. running w/o refrigerant in the system will burn out your compressor..

mvvette97

Great thanks alot. I wasn't gunna run it but just wanted to make sure the clutch was ok on the compressor. I was just thinking there may be something wrong with the wiring or something