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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different car >> Section 79 (HVAC - Manual) >> Diagnostic Information and Procedures >> Air Delivery Improper - Auxiliary >> Circuit/System Testing

Circuit/System Testing

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Mode Malfunction - Front Auxiliary Control

  1. Ignition OFF, disconnect the harness connector at the front auxiliary HVAC control assembly.
  2. Ignition ON, verify a test lamp illuminates between the ignition circuit terminal J and ground.
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  3. Ignition OFF, connect the harness connector at the front auxiliary HVAC control assembly. Disconnect the harness connector at the auxiliary HVAC control assembly.
  4. Ignition ON, test for ignition voltage between the signal circuit terminal E and ground.
    • If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the front auxiliary HVAC control assembly.
  5. Ignition OFF, connect the harness connector at the auxiliary HVAC control assembly. Disconnect the harness connector at the auxiliary mode actuator.
  6. Test for less than 5 ohms between the ground circuit terminal 7 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 10 and ground.
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  8. Install a DMM between the control circuit terminal 8 and ground. Command the actuator in each direction. Voltage on the control circuit should change from 0 volts when commanding the actuator in one direction to 12 volts in the other direction.
    • If the voltage does not change as specified, replace the auxiliary HVAC control assembly.
  9. If all circuits test normal, test or replace the auxiliary mode actuator.

Mode Malfunction - Rear Auxiliary Control

  1. Ignition OFF, disconnect the harness connector at the rear auxiliary HVAC control assembly.
  2. Test for less than 5 ohms between the ground circuit terminal B and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify a test lamp illuminates between the ignition circuit terminal G and ground.
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  4. Ignition OFF, connect the harness connector at the front auxiliary HVAC control assembly. Disconnect the harness connector at the auxiliary HVAC control assembly.
  5. Ignition ON, test for ignition voltage between the signal circuit terminal D and ground.
    • If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the rear auxiliary HVAC control assembly.
  6. If all circuits test normal, replace the auxiliary HVAC control assembly.

Mode Malfunction without Rear Auxiliary Control

  1. Ignition OFF, disconnect the harness connector at the front auxiliary HVAC control assembly.
  2. Ignition ON, verify a test lamp illuminates between the ignition circuit terminal G and ground.
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  3. Ignition OFF, connect the harness connector at the front auxiliary HVAC control assembly. Disconnect the harness connector at the auxiliary mode actuator.
  4. Test for less than 5 ohms between the ground circuit terminal 7 and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  5. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 10 and ground.
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  6. Install a DMM between the control circuit terminal 8 and ground. Command the actuator in each direction. Voltage on the control circuit should change from 0 volts when commanding the actuator in one direction to 12 volts in the other direction.
    • If the voltage does not change as specified, replace the front auxiliary HVAC control assembly.
  7. If all circuits test normal, test or replace the auxiliary mode actuator.
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