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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> HVAC - Automatic >> Diagnostic Information and Procedures >> Air Temperature Malfunction >> Circuit/System Testing

Circuit/System Testing

Sun Load Sensor Circuit Malfunction 

  1. Ignition OFF, disconnect the harness connector at the Sunload Sensor.
  2. Test for less than 1.0 ohm between the ground circuit terminal C and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify the appropriate scan tool Sunload Sensor parameter is greater than 4.9 volts or 250 counts.
    • If less than the specified range test the appropriate signal circuit terminal A or B for a short to ground. If the circuit tests normal, replace the HVAC control module.
  4. Install a 3-amp fused jumper wire between the appropriate signal circuit terminal A or B and the ground circuit terminal C. Verify the scan tool Sunload Sensor parameter is less than the 0.1 volt or 5 counts.
    • If greater than the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  5. If all circuits test normal, test or replace the sunload sensor.

Ambient / Inside Air Temperature Sensor Circuit Malfunction 

  1. Ignition OFF, disconnect the harness connector at the appropriate temp sensor.
  2. Test for less than 1 ohm between the low reference circuit terminal B and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  3. Ignition ON, verify the appropriate scan tool Temp Sensor Voltage parameter is greater than 4.9 volts or 250 counts.
    • If less than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the HVAC control module.
  4. Install a 3-amp fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool Temp Sensor Voltage parameter is less than 0.1 volt or 5 counts.
    • If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  5. If all circuits test normal, test or replace the appropriate temp sensor.

Duct Temperature Sensor Circuit Malfunction 

  1. Ignition OFF, disconnect the harness connector at the appropriate temp sensor.
  2. Test for less than 1.0 ohm between the low reference circuit terminal A and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  3. Ignition ON, verify the appropriate temp sensor parameter is greater than 4.9 volts or 250 counts.
    • If less than the specified range, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the HVAC control module.
  4. Install a 3-amp fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal B. Verify the scan tool temp sensor parameter is less than 0.1 volt or 5 counts.
    • If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  5. If all circuits test normal, test or replace the appropriate temp sensor.
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