LEMON Manuals: Even more car manuals for everyone
Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> HVAC - Automatic >> Diagnostic Information and Procedures >> Air Conditioning Compressor Malfunction >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector X1 terminal A8 ground circuit terminal at the HVAC control module.
  2. Ignition OFF, test for less than 1.0 ohm of resistance between the ground circuit terminal and ground.
    • If greater than the specified, test the ground circuit for an open/high resistance.
  3. Remove the A/C compressor clutch relay.
  4. Verify that a test lamp illuminates between the relay coil B+ circuit terminal 85 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  5. Verify that a test lamp illuminates between the relay switch B+ circuit terminal 30 and ground.
    • If the test lamp does not illuminate, test the relay switch B+ circuit for an open/high resistance. If the A/C clutch fuse is open, test the relay switch control circuit for a short to ground. If all circuits test normal, test or replace the A/C compressor clutch.
  6. Disconnect the harness connector at the A/C compressor clutch.
  7. Ignition OFF test for less than 1.0 ohm of resistance between the A/C compressor ground circuit terminal A and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  8. Connect the harness connector at the A/C compressor clutch.
  9. Connect a 10-amp fused jumper wire between the relay switch B+ circuit terminal 30 and the relay switch control circuit terminal 87. Verify the A/C compressor clutch engages.
    • If the A/C compressor clutch does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the A/C compressor.
  10. Connect a test lamp between the relay control circuit terminal 86 and the relay coil B+ circuit terminal 85.
  11. Using a scan tool, command the A/C relay output ON and OFF. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp remains ON all the time, test for a short to ground on the control circuit connector X2 terminal 43. If the circuit tests normal, replace the ECM.
    • If the test lamp remains OFF all the time, test for a short to voltage or an open/high resistance on the control circuit. If the circuit tests normal, replace the ECM.
  12. If all circuits test normal, test or replace the A/C compressor.
scientia non olet · About LEMON Manuals