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On this car, the A/C clutch disengages after about 5 to 10 minutes running when outside temperature is above approximately 95 deg F. A/C cools fine when the clutch is engaged.
Pressure at service port measures 42. When the A/C has cut out, jumpering the low pressure switch does not engage the compressor. The Volvo factory manual suggests that there is a temperature switch that opens the circuit when the temperature climbs above 105 deg C. There is no information about the location of this switch. Their drawing shows a wire going into the back of the compressor and coming out again, then going on through a diode block to the compressor clutch. However, on this car, there are no wires going into the back of the compressor (or anywhere, that I can see). The wiring diagram shows an internal switch in the back of the compressor. The power wire on my car appears to go directly from the wiring harness to the diode block (assuming the black box on the side of the compressor at the front is the diode and not the temp switch) and then on to the clutch.
Was this etmp switch feature eliminated on later cars?
Any suggestions on how to diagnose this? When the manual talks about "temperature above 105 deg C", are they talking about the temperature of the compressor, the refrigerant, or the engine coolant?
I have heard that, if this temperature switch is bad, there is a way to eliminate it from the circuit. That's what I did with my last car, which had such a switch in the upper radiator hose, which I replaced with a 3000 ohm resistor.
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