2003 Silverado A/C Help

[75sierraclassic]

I just bought a 2003 Silverado LS with 160,000 miles. The A/C has been giving me fits. Sometimes the compressor will turn on sometimes it won't. The A/C button in the cab is sticky but the light on the button comes on every time I push the button to turn on and turns off when I turn it off. It seems to turn on when the truck is cool but if you shut the truck off and turn it back on when its hot (with the A/C button still on) the compressor won't kick on. I put some hoses on it and took pressure readings but I'm not sure what they should be. See below. Ambient temperature was in the low 90's. I ran it for about 10 minutes and the compressor never cycled.


Engine RPM: Idle 600
Low side PSIg: 62
High side PSIg: 320
Cooled Interior Air Temp F:66

Engine RPM: 1500
Low side PSIg: 290
High side PSIg: 45
Cooled Interior Air Temp F:56

Engine RPM: 2000
Low side PSIg: 45
High side PSIg: 280
Cooled Interior Air Temp F:58

I tried to jump the low side pressure switch when the compressor wouldn't turn on and it still didn't turn on. I havent tried to jump the high side switch.

Any thoughts on what it could be?