Low Pressure Sensor / Switch: Testing and Inspection

Before performing diagnosis of the low pressure clutch cycling switch, be certain that the switch is properly installed on the accumulator fitting. If the switch is too loose it may not open the Schrader-type valve in the accumulator fitting, which will prevent the switch from correctly monitoring the refrigerant system pressure.

Also verify that the refrigerant system has the correct refrigerant charge. Refer to Refrigerant System Charge Test for the proper procedures.
1. Disconnect and isolate the battery negative cable.
2. Disconnect the headlamp and dash wire harness connector from the low pressure clutch cycling switch on the accumulator fitting.
3. Install a jumper wire between the two cavities of the headlamp and dash wire harness connector for the low pressure clutch cycling switch.
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 clutch cycling switch. There should be continuity with a suction pressure reading of 262 kPa (38 psi) or above, and no continuity with a suction pressure reading of 141 kPa (20.5 psi) or below. If OK, test and repair the A/C switch sense circuit as required. If not OK, replace the faulty switch.