My AC just quit today. Fortunately it was only about 95 today in Florida.
The compressor randomly disengaged several times while driving during the day and then after getting home it refused to engage again at all.
I checked the 7.5A "MG Clutch" fuse in the underhood relay box. It was fine. I also removed the AC clutch relay. I first tested the relay. It actuates and the contact pins short and open properly when energized from a 12V source. So, the relay is not the problem. I checked the clutch contacts in the relay box. One side is 12V all the time with the car on or off. This is the normal behavior as I understand it. The other contact shows completely open between the contact and ground.
I tried shorting the 12V pin to the other contact pin to manually actuate the compressor clutch but nothing happened. I assume this could indicate one of two things depending on how the pressure switch is located in the circuit.
1 - IF, the hi/lo pressure switch is actually in series with the 2nd relay contact that leads to the compressor clutch, then the pressure switch could be bad or the compressor clutch could be bad.
2 - IF the hi/lo pressure switch only effects the control signal (coil side) of the compressor relay and is NOT in series with the clutch itself then my contact shorting test above proved that the compressor clutch is wide-open and thus bad.
I did find this reference to the 2005 which is probably identical to the 2007 circuit but I'm not sure.
"Bridging pins 1 and 2 on the compressor clutch relay circuit (pull out the relay and put in a jumper) should engage the clutch. If you do this with the engine running, you should see the compressor start to turn...don't run it long. This is the definitive test of the clutch itself as there is nothing else between the clutch and the control circuit from pin 2 of the relay box."
Could somebody help me clear this up? I don't know where the pressure switch fits in the schematic and so I don't know which assumption above is correct. If the above quote about the 2005 is also accurate for the 2007 then my question is answered and the clutch is surely bad.