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Home >> GMC >> 2007 >> Acadia SLT, AWD >> Repair and Diagnosis >> Body & Frame >> Windows >> Fixed & MOVEABLE Window Systems >> Diagnostic Information and Procedures >> Rear Window Defogger Malfunction >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, disconnect the RR DEFOG relay.
  2. Ignition OFF, test for less than 1.0 ohm of resistance between terminal 85 and ground.
    • If greater than the specified range, test for an open/high resistance.
  3. Ignition ON, verify that a test lamp does not illuminate between terminal 30 and ground.
    • If the test lamp illuminates, test the control circuit for a short to voltage
  4. Verify that a test lamp illuminates between the terminal 87 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the RR DEFOG circuit fuse is open, test terminal 30 for a short to ground.
  5. Ignition OFF, disconnect the harness connector X2 at the rear window defogger grid.
  6. Ignition OFF, test for less than 1.0 ohm of resistance between the rear window defogger grid ground circuit terminal A and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector X2 at the rear window defogger grid.
  8. Ignition ON, connect a 40-A fused jumper wire between terminal 87 and the terminal 30. Verify the rear window defogger grid is activated.
    • If the rear window defogger grid does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the rear window defogger grid.
  9. Connect a test lamp between terminal 86 and terminal 85.
  10. Command the rear defogger grid 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 voltage. If the circuit tests normal, replace the HVAC control module.
    • If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  11. If all circuits test normal, test or replace the RR DEFOG relay
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