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 HVAC controls, the desired air temperature flap position can be put in. The selected value is sent to the HVAC control module via 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 moves the temperature 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 HVAC - Manual

Connector End View Reference

Component Connector End Views Sunshade - Left (DH6)

Description and Operation

Manual HVAC Description and Operation HVAC - Manual

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 Control Module References for scan tool information

Circuit/System Verification

1. 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 B3933 HVAC - Manual.

• If within the specified range

2. 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.

• If the A/C compressor can be activated or deactivated

3. Verify the engine reaches its operating temperature.

Circuit/System Testing

1. Ignition ON, turn the temperature knob in all positions. Verify the scan tool Left Temperature Knob Position parameter. The reading should correspond to the selected temperature.

• If not the specified value
Replace the A26 HVAC Controls.

• If the specified value

2. Replace the M6 Air Temperature Door Actuator and verify the M6 Air Temperature Door Actuator can be put into all positions.

• If the M6 Air Temperature Door Actuator cannot be put into all positions
Replace the K33 HVAC Control Module.

• If the M6 Air Temperature Door Actuator can be put into all positions

3. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Heater and Air Conditioning Control Replacement Heater and Air Conditioning Control Replacement

* Control Module References Control Module References for HVAC control module replacement, programming and setup