For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage
--- | --- | --- | --- | ---
Recirculation Door Control Circuit A | 1 | 1 | 1 | 1
Recirculation Door Control Circuit B | 1 | 1 | 1 | 1
5-Volt Reference | 1 | 1 | 1 | 1
Recirculation Door Position Signal | -- | 1 | 1 | 1
Recirculation Actuator Low Reference |  | 1 | 1 | --
B+ circuit of the HVAC control module | 1 | 1 | 1 | --
Ground circuit of the HVAC control module | -- | 1 | 1 | --
1. Recirculation Actuator Inoperative

### Circuit/System Description

The recirculation actuator is a 5-wire bi-directional electric motor that incorporate a feedback potentiometer. Low reference, 5-volt reference, position signal, and 2 control circuits enable the actuators to operate. The control circuits use either a 0 or 12-volt value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds one of the control circuits while providing the other with 12 volts. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. This gives the actuator the power to adjust the air source being used from fresh air to recirculation (cabin air). When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts.

### Reference Information

#### Schematic Reference

HVAC Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

• | Air Delivery Description and Operation

• | Air Temperature Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for Scan Tool Information

### Circuit/System Verification

1. Turn ON the ignition, with the engine OFF.
2. Place the blower motor switch at the maximum speed position.
3. Place the mode switch in the vent or panel position.
4. Place the recirculation switch in the recirc position.
5. Place the recirculation switch in the fresh air position.
6. Observe the air inlet door commanded parameter in the scan tool.

The scan tool air in let commanded counts parameter should change.

### Circuit/System Testing

1. Ignition OFF, disconnect the recirc actuator harness connector at the recirculation actuator.
2. Ignition OFF, test for less than 1.0 ohm of resistance between the low reference circuit terminal 1 and ground.

⇒ | If greater than 1.0 ohm, 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 to 5.2 volts between the 5-volt reference circuit terminal 3 and ground.

⇒ | If less than 4.8 volts, 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 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.

4. Verify the appropriate scan tool parameter is less than 3 counts.

⇒ | If greater than the specified range, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the HVAC control module.

5. Install a 3 A fused jumper wire between the signal circuit terminal 2 and the low reference circuit terminal 1. Verify the appropriate scan tool actuator parameter is greater than 250 counts.

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

6. Connect a test lamp between control circuit A terminal 5 and control circuit B terminal 6.
7. Command the actuator in both directions with a scan tool (air inlet door command). The test lamp should turn ON and OFF with each command.

⇒ | If the test lamp remains always ON or always OFF during either commands, test for an open, short to ground, or short to voltage on either control circuit. If the circuit tests normal, replace the HVAC control module.

8. If all circuits test normal, replace the recirculation actuator.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Control Module References for HVAC replacement, setup, and programming.

• | Recirculation Actuator Replacement