Volvo: 1995 Volvo 850 Turbo A/C Issue, electronic climate control, magnetic clutch

Question
I have a 1995 Volvo 850 Turbo Sedan with the Electronic Climate Control (ECC).

The trouble is, when my car has been sitting for some time (>60 minutes or so) the A/C system works perfectly.  Then, after a few minutes, the system shuts the compressor off, and won't turn it back on until the car sits for a while more.  This leads me to believe that it is heat related, but it also happens during the cooler months.  Now, in diagnosing this myself, and finding myself stumped, when I turn the A/C switch off, the engine's idle speed lowers as it's supposed to.  And when I turn it back on, the idle speed raises again and the radiator fan comes on (if it's warm).  Which leads me to believe that it's a computer/control problem or something.  Please help me.

Dan Kelly

Answer
Dan,
When this happens see if there is power going to the compressor. If there is then I would say that the compressor is bad. What tends to happen is the gap on the clutch become to great and the electro magnetic clutch can not engage the compressor. There is also a temp sensor on the compressor. In the event that the compressor is overheating the switch cuts off power to the compressor. With that it is common practice to "by-pass" the sensor. It seems as if the sensor setting are set too low.