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 |
|---|---|---|---|---|
Air Temperature Door Control A Circuit | 1 | 1 | 1 | 1 |
Air Temperature Door Control B Circuit | 1 | 1 | 1 | 1 |
5-Volt Reference | 1 | 1 | 1 | 1 |
Air Temperature Door Position Signal | -- | 1 | 1 | 1 |
Air Temperature 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. Air Temperature Actuator Inoperative | ||||
Circuit/System Description
The air temperature 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 volt. 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. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts.
Diagnostic Aids
Observe the air delivery operation using the following operation:
- Ignition ON, engine ON, blower motor switch in the MAX speed position
- A/C switch in the ON position
- Mode switch in the Panel or Bi-Level position
- Press the recirculation switch, press the outside air switch
| ⇒ | Observe the recirculation door for proper movement to the recirc position. If the movement is not correct refer to Air Delivery Improper . |
Observe the following operation for proper A/C compressor operation:
- Blower motor switch in the Max speed position
- Mode switch in the Vent or Heater position
- Temperature switch in the warmest position
| ⇒ | If the A/C compressor still operates, refer to Air Conditioning Compressor Malfunction . |
Observe the blower motor operation at various and desired speeds. If the speeds are not correct, refer to Blower Motor Malfunction .
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 |
| • | Inspect the air temperature actuator, door, and any attaching linkage for binding or a condition that prevents drive shaft rotation. |
Inspect the cooling system for the following conditions:
| • | A low coolant level |
| • | A loose or worn accessory belt |
| • | A leaking radiator hose or heater hose |
| • | A kinked radiator or heater hose |
| • | A missing radiator cap pressure seal |
| • | A leaking radiator cap |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
- Ignition OFF, disconnect the recirc actuator harness connector at the air temp actuator.
- Test for less than 1.0 ohm of resistance between the low reference circuit terminal 1 and ground.
- Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 3 and ground.
- Verify the appropriate scan tool parameter is less than 3 counts.
- Install a 3A 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.
- Connect a test lamp between control circuit A terminal 5 and control circuit B terminal 6.
- Command the actuator in both directions with a scan tool. The test lamp should turn ON and OFF with each command.
- If all circuits test normal, replace the actuator.
| ⇒ | 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. |
| ⇒ | 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 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module. |
| ⇒ | 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. |
| ⇒ | 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. |
| ⇒ | 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. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for HVAC control module replacement, setup, and programming |
