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.

For circuit descriptions and diagrams, refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds.
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 to 172 kPa (15 to 25 psi) or above, and no continuity with a suction pressure reading of 48 to 90 kPa (7 to 13 psi) or below. If OK, test and repair the A/C switch sense circuit as required. If not OK, replace the faulty switch.