A/C Clutch Wiring Issue - Guru with Wiring Diagrams Needed

[Dave Adkins]

Okay, this is a boring post for sure, but I need a hand troubleshooting my 1998 RT/10's air conditioner compressor clutch. If anyone out there has the wiring diagrams and is bored enough to help, I'm in your debt.

<font color="brown"> PROBLEM: </font> Intermittent A/C clutch engagement even when switch is commanded on. 50% of the time it works fine.

<font color="brown"> Root Cause: Extensive troubleshooting reveals that the A/C clutch is not receiving it's ground signal all the time.

Attempted fixes that have failed:</font>
Replace A/C clutch relay in fuse box
Replace A/C clutch fuse in fuse box, even though the original was fine.

<font color="brown">Notes:</font>
1) There are two wires that go into the top of the A/C compressor, one is for +12VDC (a blue wire) the other is -12VDC (a black wire). The blue wire will get a +12VDC signal when the A/C is commanded on via the dash control knob, but the -12VDC wire will not *always* get a ground. There's no rhyme or reason to when it decides to crap out.

2) When it does get the ground signal from the PCM, the A/C works fine.

3) The system is absoultely properly charged, no R-134a leaks, etc. etc.

4) If I add a ground signal to the black wire when the failure mode occurs, then the A/C clutch engages just fine.

QUESTION: What is the path to ground for this $^&amp;#* black wire? I'm wondering what sensor is intermittently failing that is not allowing the PCM to provide the prpper signal. Anybody out there with the right wiring diagram?

[WESTCOAST JASON]

Is the ground that is attached to the AC mounting bolt in good condition and present?

[Johann]

The A/C clutch receives its ground from the compressor clutch relay which is controlled by the PCM. The blue power wire is hot anytime the ignition switch is in the run position.

The PCM supplies a ground path for the clutch depending on the position of the A/C switch, the thermostatic switch and the dual pressure cut-out switch all three of which are wired in series; a fault in any of the switches will interrupt the ground path.

When the system is in the failure mode, you need to check continuity through the three switches in question. A book would be invaluable.