Pontiac Repair: Air Conditioning, 1990 pontiac 6000, pontiac 6000

Question
The Air conditioner on my son's 1990 Pontiac 6000 se 3.1 liter V6 does not turn on.  It worked great last year.  When the controls are put in AC position nothing happens.  The AC clutch does not engage and the radiator fan stays off.  I also do not detect any change in engine idle speed.  I checked the recharge valve and there seems to be plenty of pressure.  I checked the AC switch in the dash board and it seems fine but I don't get a reading from one of the wires that goes to that switch indicating that the other end of it might not be connected.  Don't know what to check next.

Answer
first thing to check would be the pressure at the charge port if the pressure is not correct the clutch will not engage.next i would get a test light and check for power at the plug in on the compressor.if there is no power to the compressor there could be a relay between the switch and the compressor not functioning or there may be a broken wire.if there is power to the compressor but it does not kick in the thermostat or low pressure switch could be fault.best thing to do is get a manual on your particular model and check the wiring diagrams for your specific application.this will tell you locations of the switches and relays.