I just finished 'repairing' my girl friend's AC. I replaced the compressor b/c it wasn't engaging and repaired a leak in the pressure lines where they attach. Also replaced the acculmulator which lead to twisting and eventually replacing the evaporator. After much headache I finished and vacuumed the system down to ~29.5 for 45min. Held solid vac. I charged the first can of r134-a and when I went to engage the compressor for the first time I got nothing.....

My pressure on both sides is reading ~80 psi.vI live in Florida and that is very near the ambient air temperature.


During the initial 'repair' I replaced the low pressure switch and right now I pull the connector that attaches to the top of the compressor near the cluth and I read 13.9 volts. I bought this as a NEW compressor and I am having a hard time condemning it as bad. Can anyone shed some light on this situation? Any suggestions?

 

In the harness connector at the compressor clutch there are 2 wires:
The dark green wire comes from the compressor relay located on the firewall and it supplies the clutch with battery voltage. That's the wire you're showing battery voltage on, as it should. The other wire is black and it grounds at the rear of the driver side cylinder head. Unplug the connector at the clutch and check resistance on the black wire to battery negative, must be less than 5 ohms. If resistance is good, the clutch is bad.

 

I trace the black wire and it connects to green with a diode. I pushed pins through both green and black near the plug and if I short black to ground compressor will run and was able to charge. I turned ac off and on and the conpressor turned off and on. Even turned off the truck and started it again and the compressor engaged w/o the jump but if I let it sit for a few minutes and it won't start again with out a 'jump start' with the grounding. Will check resiatance on black wire. Any ideas??

 

Black & green should not be connected to each other. The diode will not affect the resistance to ground. The plug must be disconnected from the clutch field when measuring resistance.

 

Measures resistance and it was 138 ohms to ground.

 

There's the problem. From the terminal in the connector to battery negative the black wire must be less than 5 ohms. Splice a new wire close to the connector, to a good clean ground on the engine.

 

Traced black it goes into larger wire harness bundle on passanger side

 

Black wire feeds to PCM

 

When I connect to ground should I do it on the back side of the diode? Or can I connect close to the connector and put it under one of the compressor bolts?

 

One side of the diode splices to the green wire about 3" from the clutch connector. The other side of the diode splices to the black wire, also about 3" from the clutch connector. When you add the new piece of wire to the black one, splice it as close as possible to the connector. The other end of the added wire can go to the compressor mounting bolt.