Air Recirculation Malfunction
Air Recirculation 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
The desired position of the recirculation flap can be set with the recirculation switch and the fresh air switch at the Radio/HVAC control. 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 - Manual)
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 Verification
1. Ignition ON, press and release the Front Defrost switch. Verify the scan tool Front Defrost Switch parameter changes between Active and Inactive.
• If not the specified value, replace the A20 Radio/HVAC Control.
2. Press and release the recirculation switch. Verify the scan tool Air Recirculation Mode Switch parameter changes between Active and Inactive.
• If not the specified value, replace the A20 Radio/HVAC Control.
3. Without heated seats: Press and release the fresh air switch. Verify the scan tool Fresh Air Switch parameter changes between On and Off.
• If not the specified value, replace the A20 Radio/HVAC Control.
4. Command the recirculation door actuator in both directions with a scan tool. The scan tool Air Recirculation 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.
5. If all tests normal, replace the K33 HVAC Control Module.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the M46 Recirculation Door Motor.
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 M46 Recirculation Door Motor 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 M46 Recirculation Door Motor.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Air Inlet Valve Actuator Replacement (Air Inlet Valve Actuator Replacement)
* Radio Control Assembly Replacement (Radio Control Assembly Replacement)
* Control Module References (Programming and Relearning) for HVAC control module replacement, setup, and programming