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 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 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 ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
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 (Programming and Relearning)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 (B3933)
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)
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 be between -7 to +7 and change with the knob position. At the left end position the reading should be 16 and at the right end position -16.
• If not the specified value, replace the A26 HVAC Control
2. If all circuits test normal, 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.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Temperature Valve Actuator Replacement (Temperature Valve Actuator Replacement)
* Heater and Air Conditioning Control Replacement (Heater and Air Conditioning Control Replacement)
* Control Module References (Programming and Relearning)for HVAC control module replacement, setup, and programming