Low Pressure Cut-Off Switch

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. See Refrigerant System Charge in the Service Procedures for more information.

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. See Refrigerant System Service Equipment and Refrigerant System Service Ports in the Description and Operation for more information.
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 89.6 to 186.1 kPa (13 to 27 psi) or above, and no continuity with a suction pressure reading of 68.9 kPa (10 psi) or below. If OK, test and repair the A/C switch sense circuit as required. If not OK, replace the faulty switch.