Air Delivery Improper

Air Delivery Improper

Diagnostic Instructions

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

Diagnostic Fault Information





Circuit/System Description

The HVAC control module controls the HVAC door actuators to regulate the airflow through the HVAC system. Each actuator consists of an electric motor and a potentiometer. The module supplies a low reference and 5-volt reference source voltage to the potentiometer. The HVAC control module monitors the voltage drop across the potentiometer on the door position signal circuit. When the actuator shaft rotates, the voltage on the door position signal circuit changes. The HVAC module controls the direction of the actuator door by changing the polarity of the control circuits.

Diagnostic Aids

Inspect the mode door and recirculation actuator for the following:

* A misaligned actuator.
* Broken or binding linkages or door.
* An obstruction that prevents the actuator from operating within the full range of motion.
* Missing seals to the door.

Reference Information
Schematic Reference

HVAC Schematics (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 (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning)for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the mode actuator.
2. Test for less than 1 ohm between the low reference circuit terminal 1 and ground.

• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 3 and ground.

• If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
• If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.

4. Test for 4.8-5.2 volts between the signal circuit terminal 2 and ground.

• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.
• If less then specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module.

5. Connect a test lamp between control circuit terminal 4 and control circuit terminal 5.
6. Command the mode actuator door in both directions with the HVAC controls. The test lamp should turn ON and OFF when commanded in both directions

• If the test lamp does not illuminate in both directions, test both control circuits for a short to ground or an open/high resistance. If the circuits test normal, replace the HVAC control module.

7. If all circuits test normal, test or replace the mode actuator.

Repair Instructions

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

* Heater and Air Conditioning Control Replacement (Service and Repair)
* Mode Valve Actuator Replacement (Mode Valve Actuator Replacement)