The actuators operate using 5 circuits. A 5-volt reference, low reference, signal circuit and two bi-directional 0 or 12 volt control circuits. The HVAC control module supplies a low reference and 5-volt reference to the potentiometer. The HVAC control module monitors the voltage drop across the potentiometer on the door position signal circuit. As the actuator door changes position the door position signal circuit voltage also changes. The two bi-directional control circuits enable the actuator to operate. Both circuits are set to 0 volts when the HVAC control module detects, from the feedback potentiometer, that the actuator is in the desired position. In order to move the actuator, the HVAC control module switches the appropriate control circuit to 12 volts.

Inspect the mode door and the mode actuator for the following conditions:

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, move the temperature switch from hot to cold the temperature door should match the selected position.

1. Ignition OFF, disconnect the harness connector at the appropriate actuator.
2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal 10 and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 8 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 greater than the specified range, test the 5-volt reference circuit for a short to voltage.

4. Using a DVOM verify the voltage on the signal circuit is greater than 4.8 volts.

⇒	If less than the specified range, test the signal circuit terminal 9 for a short to ground.

5. Install a 3A fused jumper wire between the signal circuit terminal 9 and the low reference circuit terminal 10. Using a DVOM verify the voltage on the signal circuit is greater than 0.2 volts.

⇒	If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance.

6. Ignition OFF, test for less than 10 ohms between the control circuit terminal 6 and ground.

⇒	If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance.

7. Ignition OFF, test for less than 10 ohms 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.

8. Connect a test lamp between control circuit terminal 5 and control circuit terminal 6.
9. Command the appropriate actuator door in both directions. The test lamp should turn ON and OFF when moved 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 HVAC control module.

10. If both circuits test normal, test or replace the actuator.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.