Volkswagen Front Wheel Drive 1974-1989 Repair Guide

Refrigerant Pressure Switch

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OPERATION



The air conditioning system incorporates 2 pressure switches; the high pressure switch and the low pressure switch. Essentially, these switches are used to sense the refrigerant operating pressures of the air conditioning system.

The low pressure switch monitors the refrigerant pressure on the suction side of the system. The low pressure switch turns off voltage to the compressor clutch coil when the pressure drops to a level that may damage the compressor.

The high pressure switch monitors the refrigerant pressure on the discharge side. When the discharge pressure moves in excess of 200-210 psi. (1379-1448 kPa), the high pressure switch closes the circuit and will cause the condenser fan to activate. When the pressure drops between, 164-174 psi. (1131-1200 kPa) the high pressure switch opens the circuit, cutting the fan off.

TESTING



If the system is low on refrigerant and the compressor clutch does not engage, unplug the low pressure switch connector and jump the terminals. If the clutch engages, the switch is operating properly. If the system pressures are nominal and the compressor clutch does not engage, unplug the switch and jump the terminals. If the compressor engages, the switch is faulty and should be replaced. If the compressor clutch still does not engage, check the terminals for battery voltage and/or a possible open circuit.

If the high pressure exceeds specified limits and the condenser fan does not activate, disconnect the high pressure switch connector and jump the terminals. If the fan operates, the switch is faulty. If the fan is still inoperative, test the condenser fan and circuit.

REMOVAL & INSTALLATION



Procedures for discharging and servicing the air conditioning system are described in General Information And Maintenance . If a refrigerant recovery/recycling machine is not available, this job should be done at the dealer or a shop that has this equipment.

The pressure switches are threaded into the refrigerant into the refrigerant lines.

  1. Properly discharge and recover the air conditioning system using a suitable recovery/recycling station.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Unplug the connector from the switch.
  6.  
  7. Unscrew the switch from the component on which it is mounted.
  8.  

To install:
  1. Seal the threads of the new switch with teflon tape.
  2.  
  3. Install the switch and engage the connector.
  4.  
  5. Connect the battery cable.
  6.  
  7. Evacuate and recharge the system. Check for leaks.
  8.  
  9. Check the switch for proper operation.
  10.  

 
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