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Air Temperature Malfunction




Air Temperature Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

Diagnostic Fault Information





Circuit/System Description

With the temperature switch at the Radio/HVAC control, the desired air temperature flap position can be put in. The selected value is sent to the HVAC control module via the LIN-Bus.

The actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5V reference, position signal, and 2 control circuits enable the actuator to operate. The control circuits use either a 0 or 12 V value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 V. In order to move the actuator, the HVAC control module grounds one of the control circuits while providing the other with 12 V. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometers adjustable contact changes the door position signal between 0-5 V. The HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, one of the control circuits is grounded. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module removes power and ground from the control circuits.

Diagnostic Aids

Check the following mechanical fault sources:

* Air distribution box
* Air distribution hoses/air distribution ducts

Reference Information
Schematic Reference

HVAC Schematics (HVAC - Automatic)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Automatic HVAC Description and Operation (HVAC - Automatic)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning)

Circuit/System Verification

1. Ignition ON, press and release the POWER switch. Verify the scan tool Front HVAC System Status parameter changes between Off and On.

• If not the specified value, replace the A20 Radio/HVAC Control.

2. Ignition ON, turn the temperature knob in all positions. Verify the scan tool Left Temperature Knob Position parameter. The reading should be between -5 to +5 and change with the knob position. At the left end position the reading should be 18 and at the right end position -18.

• If not the specified value, replace the A20 Radio/HVAC Control.

3. Command the air temperature actuator in both directions with a scan tool. The scan tool Left Temperature Door Position parameter reading should be between 5-250 counts and change during the movement.

• If not the within specified range, refer to Circuit/System Testing.

4. Measure actual inside air temperature using a thermometer. Compare this value to the scan tool Passenger Compartment Air Temperature parameter. The measured temperature should be within 5°C (9°F) difference of parameter value.

• If not within the specified range, refer to DTC B0163 or B0183 (B0163)

5. Measure actual temperature using a thermometer at each of the duct temperature sensors. Compare this value to the appropriate scan tool Duct Actual parameter. The measured temperature should be within 5°C (9°F) difference of appropriate Duct Actual parameter value.

• If not within the specified range, refer to DTC B0173, B0178, or B3933 (B0173)

6. Measure actual evaporator temperature using a thermometer. Compare this value to the scan tool A/C Evaporator Temperature Sensor parameter. The measured temperature should be within 5°C (9°F) difference of parameter value.

• If not within the specified range, refer to DTC B0173, B0178, or B3933 (B0173)

7. Observe the scan tool Sunload parameter. The reading should be between 50-1 150 W/m(2) and change with sunlight intensity.

• If not within the specified range or not change, refer to DTC B0163 or B0183 (B0163)

8. Engine is running, activate and deactivate the A/C switch. Verify the A/C compressor can be activated and deactivated.

• If the A/C compressor cannot be activated or deactivated, refer to Air Conditioning Compressor Malfunction (Air Conditioning Compressor Malfunction)

9. Verify the engine reaches its operating temperature.
10. If all tests normal, replace the K33 HVAC Control Module.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the M6 Air Temperature Door Actuator.
2. Test for less than 5 ohm between the control circuit terminal 4 and ground.

• If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal, replace the K33 HVAC Control Module.

3. Test for less than 5 ohm between the control circuit terminal 5 and ground.

• If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal, replace the K33 HVAC Control Module.

4. Connect a test lamp between control circuit terminal 5 and control circuit terminal 4.
5. Command the M6 Air Temperature Door Actuator in both directions with a scan tool. The test lamp should turn ON and OFF when commanded in both directions.

• If the test lamp remains OFF during either of the commands, test for a short to ground on either control circuit. If the circuits test normal, replace the K33 HVAC Control Module.

6. If both circuits test normal, replace the M6 Air Temperature Door Actuator

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic instructions.

* Temperature Valve Actuator Replacement (Temperature Valve Actuator Replacement)
* Radio Control Assembly Replacement (Radio Control Assembly Replacement)
* Control Module References (Programming and Relearning)

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