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A/C Pressure Switch Circuit Troubleshooting

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NOTE:
  • Do not use this troubleshooting procedure if any of the following items are operative: The A/C condenser fan, the radiator fan, or the A/C compressor. Refer to the SYMPTOM TROUBLESHOOTING INDEX .
  • Before doing any symptom troubleshooting, check for powertrain DTCs (see GENERAL TROUBLESHOOTING INFORMATION ).
  • If the blower motor does not run at all speeds, the A/C compressor will be inoperative. Before performing any other troubleshooting, repair the cause of the inoperative blower motor.
  1. Check for body DTCs using B-CAN system diagnosis test mode A troubleshooting (see TROUBLESHOOTING - B-CAN SYSTEM DIAGNOSIS TEST MODE A ).

    Are there any DTCs indicated? 

    YES  -Do the appropriate troubleshooting for the DTC indicated. ■

    NO  -Go to step 3.

  2. Refer to the PGM-FI ECU Data List.

    Is the A/C switch off? 

    YES  -Go to step 3.

    NO  - Refer to the SYMPTOM TROUBLESHOOTING INDEX . ■

  3. Disconnect the A/C pressure switch 4P connector.
  4. Turn the ignition switch to ON (II).
  5. Measure the voltage between A/C pressure switch 4P connector terminal No. 4 and body ground.
    Fig 1: Measuring Voltage Between A/C Pressure Switch 4P Connector Terminal No. 4 And Body Ground
    G05968422Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    YES  -Go to step 6.

    NO  -Go to step  20.

  6. Connect A/C pressure switch 4P connector terminal No. 4 to body ground with a jumper wire.
    Fig 2: Connecting A/C Pressure Switch 4P Connector Terminal 4 To Body Ground With Jumper Wire
    G05968423Courtesy of AMERICAN HONDA MOTOR CO., INC.
  7. Start the engine.

    Does the compressor and fans come on? 

    YES  -Go to step 8.

    NO  -Check for loose wires or poor connections at under-hood fuse/relay box connector H (18P). If the connections are good, replace the under-hood fuse/relay box (see REMOVAL AND INSTALLATION ). ■

  8. Turn the ignition switch to LOCK(O), then disconnect the jumper wire.
  9. Check for continuity between A/C pressure switch terminals No. 1 and No. 4.
    Fig 3: Checking Continuity Between A/C Pressure Switch Terminals No. 1 And No. 4
    G05968424Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Go to step 10.

    NO  -Go to step  19.

  10. Reconnect the A/C pressure switch 4P connector.
  11. Disconnect the HVAC control unit 30P connector.
  12. Turn the ignition switch to ON (II).
  13. Measure the voltage between HVAC control unit 30P connector terminal No. 12 and body ground.
    Fig 4: Measuring Voltage Between HVAC Control Unit 30P Connector Terminal No. 12 And Body Ground
    G05968425Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    YES  -Go to step 14.

    NO  -Repair the open in the wire between the HVAC control unit and the A/C pressure switch.

  14. Turn the ignition switch to LOCK (0).
  15. Measure the evaporator temperature sensor resistance between HVAC control unit 30P connector terminals No. 20 and No. 24.
    Fig 5: Measuring Evaporator Temperature Sensor Resistance Between HVAC Control Unit 30P Connector Terminals 20, 24
    G05968426Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is the resistance less than 24 kΩ? 

    YES  -Go to step 16.

    NO  -Test the evaporator temperature sensor (see EVAPORATOR TEMPERATURE SENSOR TEST ). ■

  16. Reconnect the HVAC control unit 30P connector.
  17. Turn the ignition switch to ON (II).
  18. Check that blower motor operates at all speeds.

    Does the blower motor operate at all speeds? 

    YES  -Check for loose wires or poor connections at the HVAC control unit 30P connector and at the A/C pressure switch 4P connector. If the connections are good, substitute a known-good HVAC control unit (see HVAC CONTROL UNIT REMOVAL/INSTALLATION ). and recheck. If the symptom/indication goes away, replace the original HVAC control unit. ■

    NO  -Repair the problem in the blower motor circuit. ■

  19. Check for proper A/C system pressure.

    Is the pressure within specifications? 

    YES  -Replace the A/C pressure switch. ■

    NO  -Troubleshoot the A/C pressure problem (see A/C SYSTEM TEST ). ■

  20. Disconnect under-hood relay box connector H (18P).
  21. Check for continuity between A/C pressure switch connector terminal No. 4 and under-hood relay box connector H (18P) terminal No. 3.
    Fig 6: Checking Continuity Between A/C Pressure Switch Connector Terminal 4 And Under-Hood Relay Box Connector H (18P) Terminal 3
    G05968427Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    YES  -Check for loose wires or poor connections. If the connections are good, check the grounds. If the grounds are good, replace the relay control module. ■

    NO  -Repair open in the wire between the relay control module and the A/C pressure switch. ■

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