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 test the low-pressure cutout requires isolating the liquid receiver. Closing the king valve starves the evaporator and compressor suction, causing suction pressure to drop rapidly until the low-pressure switch trips and stops the compressor.