Air Delivery Improper
Air Delivery Improper
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 defrost switch, defog switch, vent switch, BI-Level switch and the floor switch at the HVAC control, the wished air distribution 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 air distribution flap into the selected position.
Diagnostic Aids
Check the following mechanical fault sources:
* Air distribution box
* Air distribution hoses/air distributing ducts
Reference Information
Schematic Reference
HVAC Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
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 Testing
1. Ignition ON, press and release the defog switch. Verify the scan tool Front Defrost Switch parameter changes between Active and Inactive.
• If not the specified value, replace the A26 HVAC Control.
2. Press and release the vent switch. Verify the scan tool Instrument Panel Vents Switch parameter changes between Active and Inactive.
• If not the specified value, replace the A26 HVAC Control.
3. Press and release the floor switch. Verify the scan tool Floor Mode Switch parameter changes between Active and Inactive.
• If not the specified value, replace the A26 HVAC Control.
4. Press and release the defrost switch. Verify the scan tool Enhanced Defrost Switch parameter changes between Active and Inactive.
• If not the specified value, replace the A26 HVAC Control.
5. Press and release the BI-Level switch. Verify the scan tool Bi-level Switch parameter changes between Active and Inactive.
• If not the specified value, replace the A26 HVAC Control.
6. If all circuits test normal, replace the M37 Mode Door Actuator and verify the M37 Mode Door Actuator can be put into all positions. If the M37 Mode 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.
* Mode Control Cam Actuator Replacement (Mode Control Cam 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