Cold Air Does Not Come Out Even When The A/C Switch Is Pressed. The Glass Cannot Be Defogged. (Compressor Does Not Operate.)

Trouble symptom: 

Compressor does not operate after turning the A/C switch to ON and fan dial between LO and HI.

Trouble causes: 

Compressor failure

Wiring diagram: 

Air conditioning system Ref. to WIRING SYSTEM>Air Conditioning System>WIRING DIAGRAM .

Fig 1: Air Conditioning System Wiring Diagram (Glass Defogging)

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK A/C CONTROL PANEL. 
   1. Leave the vehicle under the condition at ambient temperature of 15°C (59°F) or more.
   2. Turn the ignition switch to ON.
   3. Turn the fan dial to the maximum position.
   4. Press the A/C switch.

   Is "A/C" displayed on the A/C control panel?

   • Yes  : Go to 2. 
   • No  : Replace the A/C control panel. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>Control Panel>REMOVAL .
2. CHECK EVAPORATOR SENSOR. 

   Using the Subaru Select Monitor, check [Evaporator Temperature] of the data monitor. Ref. to AIR CONDITIONER(DIAGNOSTICS)>Data Monitor .

   Does the data indicate -0.5 degree or more?

   • Yes  : Go to  4.
   • No  : Go to 3. 
3. CHECK EVAPORATOR SENSOR. 

   Check the evaporator sensor. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>Evaporator Sensor>INSPECTION .

   Is the check result OK?

   • Yes  : Go to 4. 
   • No  : Replace the evaporator sensor. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>Evaporator Sensor>REMOVAL .
4. CHECK PRESSURE SWITCH. 

   Check the pressure switch connection.

   Is the check result OK?

   • Yes  : Go to 5. 
   • No  : Repair the connector.
5. CHECK PRESSURE SWITCH. 

   Using Subaru Select Monitor, check [A/C Pressure Switch] of the data monitor. Ref. to AIR CONDITIONER(DIAGNOSTICS)>Data Monitor .

   Does the data indicate normal?

   • Yes  : Go to  10.
   • No  : Go to 6. 
6. CHECK AMOUNT OF REFRIGERANT PRESSURE. 

   Check the refrigerant pressure. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>Refrigerant Pressure with Manifold Gauge Set>PROCEDURE>CHECK REFRIGERANT GAS PRESSURE .

   Is the check result OK?

   • Yes  : Go to 7. 
   • No  : Perform repair according to refrigerant pressure inspection.
7. CHECK CONNECTOR. 

   Check poor contact of A/C control panel connector.

   Is the check result OK?

   • Yes  : Go to 8. 
   • No  : Repair the connector.
8. CHECK FUSE. 
   1. Turn the ignition switch to ON.
   2. Remove a fuse in the fuse & relay box.
   3. Check the fuse.

   Is the fuse normal?

   • Yes  : Go to 9. 
   • No  : Replace the fuse.
9. CHECK PRESSURE SWITCH SIGNAL. 
   1. Turn the ignition switch to OFF.
   2. Disconnect the A/C control panel connector.
   3. Turn the ignition switch to ON.
   4. Measure the voltage between A/C control panel connector terminal and chassis ground.

      Connector & terminal 

      (i88) No. 11 (+) - Chassis ground (-):

   Is the voltage 10 V or more?

   • Yes  : Replace the A/C control panel. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>Control Panel>REMOVAL .
   • No  :
     • Check for open or short circuit in the harness between fuse and A/C control panel.
     • Check for poor contact of pressure switch connector.
10. CHECK CAN COMMUNICATION CIRCUIT. 

    Using the Subaru Select Monitor, check [A/C Switch] of the data monitor of engine. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>Subaru Select Monitor>OPERATION>DATA MONITOR . Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>Subaru Select Monitor>OPERATION>DATA MONITOR .

    Does the data indicate ON?

    • Yes  : Go to  12.
    • No  : Go to 11. 
11. CHECK CAN COMMUNICATION CIRCUIT. 

    Perform the diagnosis for LAN system. Ref. to LAN SYSTEM (DIAGNOSTICS)>Basic Diagnostic Procedure>PROCEDURE .

    Is the check result OK?

    • Yes  : Replace the A/C control panel. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>Control Panel>REMOVAL .
    • No  : Repair it according to DTC of LAN system.
12. CHECK A/C RELAY ON SIGNAL. 
    1. Turn the ignition switch to ON.
    2. Measure the voltage between ECM connector terminal and chassis ground.

       Connector & terminal 

       Non-turbo model 

       (B134) No. 50 (+) - Chassis ground (-): 

       Turbo model 

       (B134) No. 1 (+) - Chassis ground (-):

    Is the voltage 10 V or more?

    • Yes  : Go to 13. 
    • No  :
      • Check for open or short in the harness between pressure switch and ECM.
      • Check poor contact of A/C relay connector.
      • Check the A/C relay. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>Relay and Fuse>INSPECTION .
13. CHECK A/C RELAY ON SIGNAL. 
    1. Start the engine.
    2. Turn the A/C switch to ON.
    3. Turn the temperature control dial at maximum cool position.
    4. Measure the voltage between ECM connector terminal and chassis ground.

       Connector & terminal 

       Non-turbo model 

       (B134) No. 50 (+) - Chassis ground (-):

       Turbo model 

       (B134) No. 1 (+) - Chassis ground (-):

    Is the voltage 0 V?

    • Yes  : Go to 14. 
    • No  : Replace the ECM. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>Engine Control Module (ECM) . Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>Engine Control Module (ECM) .
14. CHECK MAGNET CLUTCH POWER SUPPLY CIRCUIT. 
    1. Stop the engine.
    2. Disconnect the magnet clutch connector.
    3. Start the engine.
    4. Turn the A/C switch to ON.
    5. Turn the temperature control dial at maximum cool position.
    6. Measure the voltage between magnet clutch connector terminal and chassis ground.

       Connector & terminal 

       (F24) No. 1 (+) - Chassis ground (-):

    Is the voltage 10 V or more?

    • Yes  : Check the magnet clutch. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>Compressor>INSPECTION .
    • No  :
      • Check for open or short circuit in the harness between fuse and magnet clutch.
      • Check poor contact of A/C relay connector.
      • Check the A/C relay. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>Relay and Fuse>INSPECTION .