If your compressor has plenty of 134a it will not make the low pressure which is good, but if it has too much it will make the high pressure switch and wont engage the clutch to protect the compressor. That being said you need to check under the hood for the fan/comp Relay and see if the coil is open on it and you have 12 volts. If you want to check the clutch itself just throw a gauge on the low side to check pressure and if it is good run 12 volts to the one wire on the compressor. clutch should engage and if it does start tracing from that wire back to relay,wiring, fuse or climate control itself.