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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 >> Auxiliary 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 auxiliary blower motor.
  2. Test for less than 1 ohm of resistance between the ground circuit terminal 2 and ground.
    • If greater than 1 ohm, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 1 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 B+ circuit fuse is open, replace the aux blower motor.
  4. Ignition OFF, disconnect the harness connector at the auxiliary blower motor control module.
  5. Ignition ON, verify that a test lamp does not illuminates between the control circuit terminal 4 and ground.
    • If test lamp illuminates, test the control circuit for a short to voltage.
  6. Test for less than 1 ohm of resistance between the ground circuit terminal 2 and ground.
    • If greater than 1 ohm, test the ground circuit for an open/high resistance.
  7. Connect the auxiliary blower motor connector.
  8. Ignition ON, verity that a test lamp illuminates between the control circuit terminal 4 and ground.
    • If test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If circuit test normal replace auxiliary blower motor.
  9. Select the AUTO position on the front HVAC module.
  10. Test for 12-27 Mv between the control circuit terminal 1 and ground while adjusting the rear auxiliary HVAC control module blower from 1 to 4 bars.
    • If less than 12 Mv, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal replace the rear auxiliary HVAC module.
    • If greater than 27 Mv, test the control circuit for a short to voltage. If the circuit tests normal replace the rear auxiliary HVAC module.
  11. Test for above 10 volts while adjusting the rear auxiliary HVAC blower switch to 5 bars.
    • If less than 10 volts replace the rear auxiliary HVAC control module.
  12. Select the AUTO position on the rear auxiliary HVAC control module.
  13. Test for 12-145 Mv between the control circuit terminal 1 and ground while adjusting the front HVAC control module blower from low speed to high speed.
    • If less than 12 Mv, replace the front HVAC control module.
    • If greater than 145 Mv, replace the front HVAC control module.
  14. Place the front and rear HVAC modules in low speed.
  15. Test for 0.2--15 Mv between the signal circuit terminal 3 and ground.
    • If less than 0.2 Mv, test the signal circuit for a short to ground or an open high resistance. If the circuit tests normal replace the rear auxiliary HVAC module.
    • If greater than 15 Mv, test the signal circuit for a short to voltage. If the circuit tests normal replace the rear auxiliary HVAC module.
  16. If all circuits test normal, replace the auxiliary blower motor control module.
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