On Vista, the low pressure cut off switch monitors the refrigerant gas pressure on the suction side of the system. The switch is connected in series with the compressor and will turn off voltage to the compressor clutch coil when the monitored pressure drops to levels that could damage the compressor. The switch is located on the receiver/drier and is a sealed unit that must be replaced if faulty.
- Start the engine and allow to idle. Turn the air conditioner ON .
- Disconnect the switch connector and use a jumper wire to jump between terminals inside the connector boot.
- If the compressor clutch does not engage, inspect the system for an open circuit.
- If the clutch engages, connect an air conditioning manifold gauge to the system.
- Read the low pressure gauge. The low pressure cut off switch should complete the circuit at pressures of at least 30 psi. Check the system for leaks if the pressures are too low.
- If the pressures are nominal and the system works when the terminals are jumped, the cut off switch is faulty and should be replaced.
REMOVAL & INSTALLATION
- Disconnect the negative battery cable.
- Properly discharge the air conditioning system.
- Unplug the boot connector from the switch.
- Using an oil pressure sending unit socket, remove the switch from the receiver/drier.
- Seal the threads of the new switch with teflon tape.
- Install the switch to the receiver/drier and connect the boot connector.
- Evacuate and recharge the system. Check for leaks.
- Check the switch for proper operation.