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 C — close the 'king' valve

Closing the liquid line receiver outlet valve, commonly termed the 'king' valve, isolates the liquid inventory while allowing the compressor to pump residual refrigerant from the low side into the condenser for storage or maintenance.