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

Pumping down an air conditioning system to verify low-pressure cutout switch operation requires isolating the low side. Closing the liquid line king valve stops refrigerant flow to the evaporator, causing the compressor to evacuate the evaporator until the low-pressure control trips.