When pumping down an air conditioning system to test the low pressure cutout switch, assuming that the compressor is running, what should be done to initiate the test?

Correct Answer: Option A — close the "king" valve

Closing the king valve (liquid line service valve) isolates the condenser from the evaporator. This forces the compressor to pump refrigerant into the condenser, lowering suction pressure until the low-pressure cutout switch trips. This procedure verifies the switch's setpoint and functionality without requiring a full system evacuation.