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 | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Air Temperature Actuator Ignition | 1 | 1 | -- | -- |
Air Temperature Actuator Control | 1 | 1 | 1 | -- |
Air Temperature Actuator Ground | -- | 1 | -- | -- |
1. Air Temperature Actuator Inoperative | ||||
Circuit/System Description
The air temperature actuator is a 3-wire bi-directional electric motor. Ignition voltage, ground, and control circuits enable the actuator to operate. The control circuit uses a 0-12 volts linear-ramped signal to command the actuator movement. The 0 and 12 volt control values represent the opposite limits of the actuator range of motion. The values in between 0 and 12 volts correspond to the positions between the limits.
When the HVAC control assembly sets a commanded, or targeted, value, the control signal is set to a value between 0-12 volts. The actuator shaft rotates until the commanded position is reached. The module will maintain the control value until a new commanded value is needed.
Diagnostic Aids
Inspect the air temperature door and the air temperature actuator for the following conditions:
| • | A misaligned air temperature actuator. |
| • | Broken or binding linkages or air temperature door. |
| • | An obstruction that prevents the air temperature door from operating within its full range of motion. |
| • | Missing seals to the air temperature door. |
| • | Misaligned seals to the air temperature door. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Manual HVAC Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Ignition ON, engine running, place the blower motor switch at the maximum speed position and the mode switch in the vent or panel position.
- Rotate the temperature control switch from the full COLD position to the full HOT position. The air temperature should follow the commanded states of full HOT to full COLD.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the air temperature actuator.
- Test for less than 1.0 ohm between the ground circuit terminal 7 and ground.
- Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 10 and ground.
- Install a DMM between the control circuit terminal 8 and ground. Command the actuator in both directions. Voltage on the control circuit should change from 0 volts when commanding the actuator in one direction to 12 volts in the other direction.
- If all circuits test normal, test or replace the air temperature actuator.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. |
| ⇒ | If the voltage does not change as specified, test the control circuit for a short to voltage, short to ground, or an open/high resistance. If the circuit tests normal, replace the HVAC control module. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for HVAC replacement, setup, and programming |
