Anybody know anything about truck AC systems. Mine quit a while ago and I called for a used compressor and found one but before a buy I would like to know if thats whats wrong. I tried recharging the system but it just raises pressure on the gauge but the compressor won't start pumping. I've recharged it before and when there is enough pressure from the new coolant the compressor clutch engages. My question.... is there any other sensors or such that would cause the clutch to not kick on. I've checked fuses and they are all fine. Any ideas would be greatly appreciated.

what year, engine, manual or auto climate control? Impossible to diag without complete info. Quick test to check compressor. 1 12volt test light connected from compressor clutch wiring to ground. turn on system, does light lite? if so, compressor is at fault although unlikely. Could be main switch, low pressure or high pressure or pressure cycling switch, fuse, wiring or connections etc.

Its a 97, F-150. 4. 6 Litre. Manual climate control. I tried to run a test with the wires before and as soon as I unpluged the wires from the compressor the truck wouldn't run anymore. Is it possible it could be in the switch on the dash. I may test that first.

Key on, engine off. Test fuses #5 and #24 for power. If ok, then follow this path to find the answer. 1) Disconnect the plug from the compressor. A/C turned on, check for power ( battery voltage) on black and yellow wire. If no power,disconnect a/c pressure cycling switch connector ( right rear corner of engine compartment screwed into a cylinder with a/c lines attached) and check for power on red and yellow wire. If ok, replace switch. If no power, disconnect a/c pressure cut out switch ( right side of engine compartment screwed onto smaller a/c line) and test for power on pink wire. if ok, system is low on charge or switch is defective. If no power, remove control head form dash and test for power from purple wire ( terminal 3 ) If ok, wiring is open between dash and pressure cuttof switch, if no power, test light blue and pink wire at termina 4 of control head for power, if ok, replace control head switch, if no power,wiring is open between fuse #5 and control head.
Hope that helps ya out.

Most common failure on that vehicle is the compressor shaft seal. When freon gets low, low pressure switch will not allow compressor to turn on. I suggest you take it to a shop and pull the clutch disc off and see if the felt inside the hole is saturated with oil, if it is you will need a compressor.
PS- Your truck wouldn't run because you disconnected the crank sensor plug under the compressor. The clutch coil plug is on top of the compressor.

yeah what he said