My A/C started blowing warm air, so I picked up one of those R134a retrofit kits to recharge the system. I drained the remaining R12 (there wasn't much left) and proceded according to the instructions. The problem is that in order for the system to take in the R134, the compressor has to be on. Mine isn't. The belt spins around the wheel but the clutch does not engage on the compressor. I've read that there is a sensor that prevents the comrpessor from turning on when the refrigerant level is too low. Great.

Is there some way I can force the compressor to turn on so it will take in the refridgerant?

 

Might want to check some the A/C Control Relay might having some bugging down, most aircon parts are very complicated when running all the time.