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Home >> Isuzu >> 2007 >> i-290 LS, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 13 (HVAC System - Automatic) >> Diagnostic Information and Procedures >> Blower Motor Malfunction >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2007 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the FRT HVAC BLWR relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the B+ circuit terminal 134 and ground.
    • If the test lamp illuminates, test the B+ circuit for a short to voltage
  3. Verify that a test lamp illuminates between the B+ circuit terminal 135 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Verify that a test lamp illuminates between the B+ circuit terminal 138 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 test normal and the HVAC BLWR fuse is open, test the B+ circuit for a short to ground. If the circuit tests normal, replace the blower motor control module.
  5. Connect a test lamp between the control circuit 137 and the B+ circuit 135.
  6. Command the blower motor ON and OFF. The test lamp should turn ON and OFF when changing between the commanded states.
    • 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 HVAC control module.
    • If test lamp is always ON, test for short to ground. If circuit tests normal, replace the blower motor control module
  7. Connect the FRT HVAC BLWR relay.
  8. Disconnect the harness connector at the blower motor control module.
  9. Test for less than 1.0 ohm of resistance between the ground circuit terminal 4 and ground
    • If not the specified range, test the ground circuit for an open/high resistance.
  10. Connect a test lamp between the B+ circuit terminal 2 and ground.
  11. Turn ON the blower motor. Verify the test lamp illuminates
    • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. If the circuit tests normal, test or replace the FRT HVAC BLWR relay.
  12. Install a test lamp between the control circuit terminal 3 and B+.
  13. Turn the blower motor ON and cycle between low and high speeds. The test lamp should dimly illuminate at high speeds and reduce in intensity as the blower speed is reduced.
    • If the test lamp does not illuminate, test the control circuit for short to voltage or an open/high resistance. If the circuits test normal, test or replace the HVAC control module.
    • If the test lamp does not change intensity, test the control circuit for a short to ground. If the circuit tests normal, test or replace the HVAC control module.
  14. Connect the harness connector at the blower motor control module.
  15. Disconnect the harness connector at the blower motor.
  16. Install at test lamp between the B+ circuit terminal 1 and ground.
  17. Turn ON the blower motor. Verify the test lamp illuminates.
    • If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
  18. Install a test lamp between the control circuit terminal 1 and the low reference circuit terminal 2.
  19. Turn the blower motor ON and cycle between low and high speeds. The test lamp should illuminate and change in intensity as the blower speed is varied.
    • If the test lamp does not illuminate, test the low reference circuit for short to voltage or an open/high resistance. If the circuit test normal, test or replace the blower motor control module.
    • If the test lamp does not change intensity, test the low reference circuit for a short to ground. If the circuit tests normal, test or replace the blower motor control module.
  20. If all circuits test normal, replace the blower motor.
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