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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1944 (HVAC System - Automatic) >> Diagnostic Information and Procedures >> Air Temperature Malfunction >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

Sun Load Sensor Circuit Malfunction

  1. Ignition OFF, disconnect the harness connector at the sunload sensor.
  2. Test for less than 10 ohms 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, test for 4.8-5.2 volts between the ground circuit terminal C and the appropriate signal circuit terminal listed below:
    • Left solar load sensor circuit terminal A
    • Right solar load sensor circuit terminal B
    • If less than the specified range, test the signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the HVAC control module.
    • If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.
  4. If all circuits test normal, test or replace the sunload sensor.

Ambient Air Temperature Sensor Circuit Malfunction

  1. Ignition OFF, disconnect the harness connector at the ambient air temperature sensor.
  2. Ignition OFF, test for less than 10 ohms between the following 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 scan tool Outside Air Temp. Raw parameter is less than -35°C (-39°F).
    • If greater than the specified range, test the following signal circuit terminal A for a short to ground. If the circuit tests normal, replace the HVAC control module.
  4. Install a 3A fused jumper wire between the following signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool Outside Air Temp. Raw parameter is greater than 85°C (185°F).
    • If less 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 ambient air temperature sensor.

Inside Air Temperature Sensor Circuit Malfunction

  1. Ignition OFF, disconnect the harness connector at the inside air temperature sensor.
  2. Test for less than 1 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 a test lamp illuminates between the control circuit terminal B and ground.
    • If the test lamp does not illuminate, test the ground circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  4. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal D 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.
  5. Ignition ON, verify that the scan tool Inside Air Temp. Sensor parameter is less than -35°C (-39°F).
    • If greater 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.
  6. Install a 3A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal D. Verify the scan tool Inside Air Temp. Sensor is greater than 98°C (208°F).
    • If less 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.
  7. If all circuits test normal, test or replace the inside air temperature sensor.

Duct Temperature Sensor Circuit Malfunction

  1. Ignition OFF, disconnect the harness connector at the appropriate duct temperature sensor.
  2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal 2 listed below 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 that the appropriate scan tool Duct Actual parameter is less than -35°C (-39°F).
    • If greater 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 3A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2. Verify the appropriate scan tool Duct Actual parameter is greater than 98°C (208°F).
    • If less 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 duct temperature sensor.

Heater Core Coolant Pump Malfunction

  1. Ignition OFF, disconnect the harness connector at the heater core coolant pump.
  2. Ignition ON, verify that a test lamp illuminates between the control circuit terminal B and ground while commanding the pump ON and OFF with a scan tool.
    • If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the SGCM.
  3. Verify that a test lamp illuminates between the B+ circuit terminal A and ground.
    • If the test lamp does not light, test the B+ circuit for a short to ground, open or high resistance. If the circuit tests normal, replace the Coolant heater pump
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