mcmichael13

Hey All,

Now I've done lots of research and troubleshooting already on this issue and followed out every wire in the schematics and tested just about everything I can think of to try and pinpoint my issue.

AC refrigerant is good, compressor is good, relays are good, etc.

The compressor clutch will not engage unless I install a jumper wire in the relay. When I ground out either pin in the pressure switch the idle comes up and the condenser fan engages but the compressor clutch does not. If I jump the two wires in the connector nothing happens.
I pulled the dash apart to see if the there were any broken/loose solder joints on the heater control board and there were not though I did put some extra solder on the AC switch connections.
I do read battery voltage at pin A17 (black/red wire) at the ECM.
I also read battery voltage at pin C5 (blue/red) at the ECM.

I swapped out the ECU and for two weeks or so my AC was working as normal but then it started not engaging the clutch again. I am assuming that my previous ECM was faulty in the AC circuit and for some reason this ECM failed as well. I attempted to trace A17 back into the ECU and it goes into a power transistor array (STA415A) from what I can tell. I wanted to try and see what was failing so I could determine why two ECMs are doing the same thing when they both worked previously at separate times. Any insight or ideas?

I thought perhaps the AC Diode was faulty and voltage was flowing back into the ECU to cause failure but I believe the diode is ok (read voltage one direction and zeroed the other direction).

Any help or insight would be greatly appreciated. I've been driving myself nuts trying to figure this out.