Refrigerant Pressure Sensor / Switch: Description and Operation
A/C Pressure SwitchThe A/C pressure switch is located in the condenser outlet line where refrigerant is in a high temperature/high pressure liquid state. The A/C switch turns OFF the A/C compressor clutch if it senses abnormally high or low pressure. If the A/C pressure switch opens, and the BLU/RED wire at the A/C diode was the only wire providing ground to the condenser and radiator fan relays (A/C switch ON, heater fans switch ON, engine coolant temperature switch open, and ECM fan control output not grounded), the relay will deenergize removing voltage from the condenser and radiator fan motors causing them to stop running.