tcora

Unplug the wire and put a multimeter on it? I have seen clutches go bad.

Bush Pilot

Thank you. After looking at the schematic in the Bentley's it appears that it's simply 2 wires going to the compressor and I'm guessing that I should measure 12V between the two with the compressor commanded on. Is that correct?

tcora

Sounds about right to me!

craig2112

I would also check the AC pressure switch.

Bush Pilot

How would I check that/those?

TexSquirrel

With the engine running, do a continuity test across both terminals on the switch.
If closed, it's working, if not, then the switch is not closing either due to faulty switch, or not enough pressure.
I would caution against grounding the wires going to any sensor.
That can damage transistors from/to the computer/controller.
I've seen ECUs damaged that way many times.

Bush Pilot

I connected a refrigerant can to the system and that pressurized the system to about 28 psi, hi and lo side, per my uncalibrated Chinese gauges and the compressor did not come on so that more refrigerant would be brought into the system. Would that be enough pressure to trigger the sensor to allow the compressor to come on? Edited: Just realized that that's a dumb question since 28 psi is within the operating range so that should be enough pressure to trigger the low pressure switch to allow the compressor to come on.

craig2112

I couldn't find published anywhere what the low pressure switch trip pressure is. You could try increasing the pressure in your system by putting the refrigerant can in a bucket of hot water. I'm guessing your ambient temperature is around 32F based on the 28psi static pressure reading.

TexSquirrel

It should be enough to allow the pressure sensor to signal that the compressor can be turned on.

Bush Pilot

Where would I find the pressure switch? From my reading I would expect there to be a high pressure side switch and a low pressure side switch but when I search "air conditioning pressure switch" for my car on Pelican's site only one switch pops up and the description doesn't say what side it is which leads me to believe that I have only one ac pressure switch.

TexSquirrel

The high pressure switch is right in front of the cabin air filter and the VIN on the chassis.
Look for the high pressure connection.
It is just in front of it.

Bush Pilot

Thank you. What about a low pressure switch location?. Since my compressor won’t come on, if it is a pressure switch I’m thinking it would be a low pressure one.

TexSquirrel

I'm not certain whether there is a low pressure switch.
I have only seen the high pressure switch when attaching gauges and refilling refrigerant.
I've replaced entire AC systems in other vehicles, but not in a 986 or 986.

BTW, I just checked my wiring diagrams and I found the attached for AC wiring for the 996/997.
The 986/987 should be similar.
Part numbers for most AC components are similar between 986 & 996.

Bush Pilot

Thanks so much Tex. You're a lot of help. I've come to the conclusion that there's only one pressure switch in the system. I'm going to do some more troubleshooting this weekend. Time to get this AC working.

Gasngo

I have you found your problem yet?