Low Pressure Sensor / Switch: Testing and Inspection

Before performing diagnosis of the low pressure cut-off switch, remember that lower ambient temperatures, below about -1 °C ( 30°F), during cold weather will open the switch contacts and prevent compressor operation due to the pressure/temperature relationship of the refrigerant.

Also verify that the refrigerant system has the correct refrigerant charge.

1. Disconnect and isolate the battery negative cable.
2. Unplug the low pressure cut-off switch wire harness connector from the switch on the suction line jumper fitting.
3. Install a jumper wire between the two cavities of the low pressure cut-off switch wire harness connector.
4. Connect a manifold gauge set to the refrigerant system service ports.
5. Connect the battery negative cable.
6. Place the heater-A/C mode control switch knob in any A/C position and start the engine.
7. Check for continuity between the two terminals of the low pressure cut-off switch. There should be continuity with a suction pressure (low side) reading of 103 - 172 kPa (15 - 25 psi) or above, and no continuity with a suction pressure reading of 48 - 90 kPa (7 - 13 psi) or below. If OK, test and repair the A/C switch sense circuit as required. If not OK, replace the faulty switch.