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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G3500, VAN PASSENGER EXTENDEDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 927 (HVAC SYSTEM - AUTOMATIC)DIAGNOSTIC INFORMATION AND PROCEDURESBLOWER MOTOR MALFUNCTIONCIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G3500, Van Passenger Extended

Circuit/System Testing

2008 Chevrolet Chevy Express G3500, Van Passenger ExtendedSECTION Circuit/System Testing
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the X2 harness connector at the blower motor control module.
  2. Test for less than 1.0 Ξ© between the ground circuit terminal 5 and ground.
    • 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 terminal 6 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 (HVAC BLWR 40-amp) in the underhood fuse block is open, test all components connected to the B+ circuit and replace as necessary.
  4. Connect the X2 harness connector at the blower motor control module and connect DMM between the control circuit terminal 3 and ground.
  5. Cycle the blower motor from OFF to HIGH. The voltage should decrease while changing between the commanded states.
    • If voltage remains greater than 11.5 V 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.
    • If voltage remains less than 1.0 V 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.
    • If voltage is between 1.0-11.5 V and does not decrease when changing between the commanded states, replace the HVAC control module.
  6. Ignition OFF, connect the X2 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 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, replace the blower motor control module.
  8. Connect a test lamp between the control circuit terminal B and the B+ circuit terminal A.
  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.
    • 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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