Dual function high pressure switch/high pressure cut-off switch. Low pressure cut-off switch

Dual function high pressure switch/high pressure cut-off switch

Before performing diagnosis of the dual function high pressure switch, or the high pressure cut-off switch, verify that the refrigerant system has the correct refrigerant charge. See Refrigerant System Charge in the Service Procedures section of this group for more information.

For circuit descriptions and diagrams, refer to 8W-42 - Air Conditioning/Heater in Group 8W - Wiring Diagrams.

(1) Disconnect and isolate the battery negative cable.

(2) Unplug the high pressure switch wire harness connector from the switch on the refrigerant system fitting.

(3) On the dual function high pressure switch, check for continuity between terminals C and D. On the two terminal switch, check for continuity between both terminals of the high pressure cut-off switch. There should be continuity. If OK, test and repair the A/C switch sense circuit as required. If not OK, replace the faulty switch.

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 section of this group for more information.

For circuit descriptions and diagrams, refer to Air Conditioning/Heater in Wiring Diagrams.

(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 section of this group 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 48 to 193 kPa (15 to 28 psi) or above, and no continuity with a suction pressure reading of 90 kPa (13 psi) or below. If OK, test and repair the A/C switch sense circuit as required. If not OK, replace the faulty switch.