air conditioner problem

I have a 93 cadi sedan de ville on my hands .. The compressor has 12 volts at the connector when disconnected.. but when you connect it up to the compressor the 12 volts disapears the comp doesn t even kick? ....if I apply outside voltage to the compressor it starts and runs .... the system is charged...any ideas or wiring diagrams out there ....regards john

Replace your low pressure switch.This may solve your trouble.