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Home >> Saturn >> 2009 >> Vue Red Line, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1092 (HVAC System - Automatic) >> Diagnostic Information and Procedures >> DTC P0645 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 Saturn Outlook, 2008 GMC Acadia, and 2008 Buick Enclave. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the A/C Relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 86 and ground.
    • If the test lamp illuminates, test the control circuit for a short to voltage.
  3. Verify that a test lamp illuminates between the ignition circuit relay coil feed circuit terminal 85 and ground.
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or a open/high resistance. If the circuit tests normal and ignition circuit fuse is open, test all components connected to the ignition circuit and replace as necessary.
  4. Verify that a test lamp illuminates between the relay B+ circuit terminal 30 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or a open/high resistance. If the circuit tests normal and B+ circuit fuse is open, replace the A/C Clutch Relay.
  5. Disconnect the harness connector at the A/C Clutch Coil.
  6. Test for less than 1 ohm between the A/C Clutch Coil ground circuit terminal ground.
    • If greater than 1 ohm, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the A/C Clutch Coil.
  8. Connect a 10-amp fused jumper wire between the B+ circuit terminal 30 and control circuit terminal 87 of the A/C Clutch Relay. Verify the A/C Clutch Relay is activated.
    • If the A/C Clutch Relay does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the A/C Clutch Relay.
  9. Connect a test lamp between the coil side of the A/C Clutch Relay ignition circuit terminal 85 and the control circuit terminal 86.
  10. Command the A/C Relay output function ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
    • If the test lamp is always OFF, test the control circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the ECM.
  11. If all circuits test normal, replace the A/C Clutch Relay.
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