Auxiliary Air Temperature Malfunction

Auxiliary Air Temperature Malfunction

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

Diagnostic Fault Information







Circuit/System Description
With the temperature switches at the Radio/HVAC control - auxiliary, 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 HVAC control module supplies a 12 V reference voltage to the stepper motor and energizes the 4 stepper motor coils with a pulsed ground signal. The stepper motor puts the mixed air flap into the calculated position, in order to reach the selected temperature.

Diagnostic Aids
Check the following mechanical fault sources:
- Air distribution box
- Air distribution hoses/air distribution ducts

Reference Information

Schematic Reference
HVAC Schematics

Connector End View Reference
Component Connector End Views

Description and Operation
Automatic HVAC Description and Operation

Electrical Information Reference
- Circuit Testing
- Connector Repairs
- Testing for Intermittent Conditions and Poor Connections
- Wiring Repairs

Scan Tool Reference
Control Module References for scan tool information

Circuit/System Verification
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.

Circuit/System Testing
1. Ignition ON, press and release the rear temperature increase switch. Verify the scan tool Rear Temperature Setting parameter. The reading should correspond to the selected temperature.
2. If not the specified value, replace the A21 Radio/HVAC Controls - Auxiliary.
3. Press and release the rear temperature decrease switch. Verify the scan tool Rear Temperature Setting parameter. The reading should correspond to the selected temperature.
4. If not the specified value, replace the A21 Radio/HVAC Controls - Auxiliary.
5. Press and release the ZONE Switch. Verify the scan tool MULTIZONE Switch parameter changes between Active and Inactive.
6. If not the specified value, replace the A20 Radio/HVAC Controls.
7. If all circuits test normal, replace the M6B Air Temperature Door Actuator - Auxiliary and verify the M6B Air Temperature Door Actuator - Auxiliary can be put into all positions. If the M6B Air Temperature Door Actuator - Auxiliary cannot be put into all positions, replace the K33 HVAC Control Module.

Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Auxiliary Temperature Valve Actuator Replacement
- Heater and Air Conditioning and Radio Control Module Replacement
- Instrument Panel Lower Center Trim Panel Replacement
- Control Module References for HVAC control module replacement, setup, and programming