Low Pressure Sensor / Switch: Testing and Inspection
A/C LOW PRESSURE SWITCHBefore performing diagnosis of the A/C low pressure 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 had the correct refrigerant charge.
1. With gear selector in park or neutral and park brake set, start engine and allow to idle.
2. Raise hood and disconnect low pressure cut off switch connector boot.
3. Using a suitable jumper wire, jump across the terminals inside wire connector boot.
4. If the compressor clutch does not engage, the A/C low pressure switch, wiring, relay, or fuse can be defective.
5. If clutch engages, connect manifold gauge set. Read low pressure gauge. At pressure above 97 kPa (14 psi) and above, low pressure out off switch will complete the clutch circuit. If the low pressure gauge reads below 140 kPa (20 psi), the system is low on refrigerant charge or empty due to a leak.
6. Install connector boot on switch and repeat Step 3. If the clutch does not engage, replace the A/C low pressure switch.