My air conditioning compressor pump is not staying on long enough to cool down my truck. I have a 92 K 2500. initially the compressor turns on and off ( doesn't stay on very long) and then the compressor won't turn on at all. It behaves as though the system thinks that the temperature in the truck is cool enough even though I have turned the control all the way to the coolest temperature. If I bypass the compressor pressure switch on the condenser the compressor will stay on and the truck will cool down.

 

When my 93 did this I changed the switch on the condenser. Has needed it twice so far. Quick fix - unplug connector, unscrew the switch - protected by a valve so won't lose charge.

 

I have replace that switch and when I bypassed it the compressor stayed on and began cooling the truck.

 

Maybe I need to replace it again, I think I'm going to buy the gauges to measure the high and low pressures to see if the switch is working correctly or not. Appreciate your input.