Howdy all,

Starting in August, my AC clutch began disengaging after a few miles of driving (assumed it was due to the coil heating up). Finally it quit working altogether. I finally got around to digging into it this past week and determined the clutch was bad. I replaced the compressor/clutch assembly and it seems to be in working order now, but the clutch still won't engage through the clutch relay in the underhood fuse box. Here is where it gets weird for me. With the engine running and AC turned on:

1. I have 13V across the two relay coil terminals (seems to be getting a call for AC to the relay)
2. I have 13V across the two load terminals (voltage and ground to the clutch seem good)
3. If I jump the two load terminals the clutch engages (clutch seems to operate correctly)
4. If I swap the clutch and fan relays, the fan works with both, but the clutch works with neither (seems the relays are good)

My only thought is I'm somehow not getting good contact between the relay and the terminal but I have messed with that quite a bit to no avail. Anything else you guys can think of? I am a plumber rather than a mechanic, so it's very possible I am missing something.

Thanks,

 

See attached wiring diagram.

Your symptoms indicate the ground (enable) signal to the AC relay from ECM/PCM on pin 3 (red wire) is not being supplied. Either red wire is defective, defective ECM/PCM, or input to enable AC (pressure switch, relay module, gauge control module, or wiring) is faulty.

Suggest checking for voltage w/ a test light on pin 3 (red wire). If voltage is present, the ground signal is missing. If no voltage ground is being supplied.

good luck

 

Thanks for your help!

I do have 13V at pin 3, so it seems to be a grounding issue. I do not see a wiring diagram attached to your reply, but based on what I've researched it seems the pressure switch is part of the grounding run, is that correct? If so, how do I test a 4-pin pressure switch? All I can find online is 2 and 3 pin switches.

 

Sorry, I forgot the attachment.

Ground signal comes from PCM based on inputs, one of which is Pressure switch. See diagram.

Suggest accessing the AC control panel to see if DTC is set. See attachment.

good luck

 

So I went through the steps suggested and found a repair manual online. The clutch relay coil is not getting grounded through the PCM, correctly. Took it in and had it verified by a mechanic. They want ~$1700 to replace and program a new one. I have found many places online that claim to repair them for ~$200 with no programming necessary and a lifetime warranty. Does anyone have experience with these companies? One of them has an A+ with BBB but I can't seem to find any of the others on BBB or even find online review of them.

 

I sent out a PCM to some where in Atlanta. They did a good job for me on an 04 maxima I was fixing up for a friend. $200 sure does beat $1700. Whatever you do pay through PayPal at least you know you can get your money back if it does not work.