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Circuit/System Testing

WARNING: This page is about a different car, the 2004 Chevrolet Monte Carlo and 2004 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connector at the blower motor control module.
  2. Test for less than 1.0 ohm between the ground circuit and ground.
    1. → If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify that a test lamp illuminates between the B+ circuit and ground.
    1. → 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 (BATT 4 30-amp) in the underhood fuse block is open, test all components connected to the B+ circuit and replace as necessary.
  4. Connect a DMM between the control circuit and B+.
  5. Cycle the blower motor from OFF to HIGH. The voltage should increase while changing between the commanded states.
    1. → If voltage remains greater than 11.5V while changing between the commanded states, test the control circuit for a short to voltage. If the circuit test normal, replace the HVAC control module.
    2. → If voltage remains less than 1.0V while changing between the commanded states, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
    3. → If voltage is between 1.0V or 11.5V and does not increase when changing between the commanded states, replace the HVAC control module.
  6. Ignition OFF, reconnect the harness connector at the blower motor control module. Disconnect the harness connector at the blower motor.
  7. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal A of the blower motor control module and ground.
    1. → 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, replace the blower motor control module.
  8. Connect a test lamp between the control circuit terminal B and the B+ circuit.
  9. Turn the blower motor on high speed then to low speed. The test lamp intensity should be bright when in high speed and very dim or off when the blower is on low speed.
    1. → If the test lamp intensity does not vary, test the control circuit for a short to voltage, short to ground, or an open/high resistance. If the circuit tests normal, replace the blower motor control module.
  10. If all circuits test normal, test or replace the blower motor.
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