1993 turbo, A/C compressor

[jjmoore]

1993 K30 6.5 turbo. some times the A/C compressor will not engage the clutch.. it has full charge. when i pull the plug on compressor and measure voltage I get 13.5... when I plug it back in I get 0 .I check ohms of coil I get 3.5 ohms. I jumped coil with 12 volts from plus battery terminal.. compressor started working and stayed working .. coil voltage is 11.5 volts with a 14.1 battery voltage when running. I think I am getting a voltage drop some where , in series , in the circuit.. is there a compressor relay ? or is the power to the clutch coil go thru the A/C control in the dash?

[DmaxMaverick]

The circuit goes through the dash control head (fused, ign/acc leg), to a relay, to the coil. Your voltage drop is too much, even with the (anemic) small wire. You're losing voltage, somewhere. Probably a connector (or several) at some point. Heat makes them worse, and we seldom worry about the A/C when it isn't hot.

[THEFERMANATOR]

Low ressure switch is where I would start. On early trucks GM had teh bright idea of running the compressor power through the low pressure switch instead of using teh switch to trigger teh relay.