New Compressor Installed-Clutch not turning on-whats wrong? - Page 3 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat
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Old 08-14-2006, 06:05 PM   #21
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Default Re: New Compressor Installed-Clutch not turning on-whats wro

Just checking back in to see how it'* going.

I did find a wiring diagram for a '93. It'* a bit different than my 90.

First, I have three pressure switches, yours only has two. (Cycling switch on the accumulator and High Pressure Cutout on the back of the compressor)

2nd, My ECM only gets feedback from the switches to know when the compressor is running and kicks high idle. Yours has a PCM that reads the pressure switches on one circuit, then commands the clutch on a seperate circuit. That explains why your wires are going into the dash.

So, in a nutshell, the switches tell your PCM that conditions are right to turn on the AC compressor. Then the PCM activates the relay that is connected to the clutch.

Also, according to the wiring diagram, you have another fuse in the "Relay Center" that is only used to run the AC clutch and it'* relay.

Those two pink wires in the relay socket are actually on the same circuit and lead back to that 15Amp fuse. And you should be able to test +12VDC on them whenever the ignition is in the run position.

The Dark Green wire comming out of the relay socket is supposed to go straight to the compressor clutch (and also to a diode). Put +12VDC to that wire and the clutch should come on.

The Light green wire (or Drk Green with White Stripe) is going to the PCM. That'* the wire the PCM grounds out to activate the relay.

On the switches, You got a light green wire comming through the firewall from the heater/AC control unit (***** and dash switches) that leads to the High Pressure Cutout switch on the compressor. The blue wire from that switch goes back to the Cycle switch on the Accumulator. The other post on that switch (also shown as a dark blue wire in the diagram) leads back through the firewall to the PCM,
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Old 08-14-2006, 11:20 PM   #22
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Wow Curt...thank you for the info. I should have my hands on a multi-meter tomorrow, and hopefully be able to trace out where this problem is coming from.

I certainly couldn't have done this without your help, and I want you to know I appreciate it. I chime in again tomorrow night and let you know how this pan out. With any luck, by the end of this week i'll have a frigid AC system in my car. Thanks again Curt.

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