Various cars have various switches connected to the A/C lines. If the refrigerant pressure is too low, it will shut off the compressor. If the pressure is too high, it will shut off the compressor.

You need to have just the right amount of refrigerant - not too much, not too little, THEN the switch will allow the compressor to run.

So look for those sort of switches - usually around the accumulator/receiver/dryer.