Air Temperature Malfunction
Air Temperature Malfunction
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 temperature actuators are a 5-wire bi-directional electric motors 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. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts.
Diagnostic Aids
Inspect the appropriate temperature 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
* Air Delivery Description and Operation (Air Delivery Description and Operation)
* Air Temperature Description and Operation (Air Temperature Description and Operation)
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 appropriate air temperature 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 to 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 door position 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 temperature 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 the control circuits for a short to ground or an open/high resistance. If the circuit tests normal replace the HVAC control module.
7. If all circuits test normal, replace the appropriate temperature actuator.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Air Temperature Actuator Replacement - Right Side (Air Temperature Actuator Replacement - Right Side)
* Air Temperature Actuator Replacement - Left Side (Air Temperature Actuator Replacement - Left Side)
* Heater and Air Conditioning Control Replacement (Service and Repair)