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Too Hot In Vehicle



Too Hot in Vehicle

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* 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/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 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

Air Conditioning (A/C) System Performance Test

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.

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 Air Temperature switch in the full COLD position.
5. Place the Air Temperature switch in the full HOT position.

The flow of air should change through the vent or panel.

Circuit/System Testing

1. Ignition OFF, disconnect the air temperature actuator harness connector at the air temperature actuator.
2. Ignition OFF, test for less than 1.0 ohm of resistance between the low reference circuit terminal A11 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 A9 and ground.

• If less than 4.8 volts, test the 5-volt reference circuit terminal A9 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. Install a 3-amp fused jumper wire at the signal circuit terminal A10, test for greater than 5 volts. Toggle the jumper wire between the low reference circuit terminal A11 and the 5-volt reference circuit terminal A9.

• If the position signal parameter is less than 5 volts, test the signal circuit terminal A10 for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the HVAC control module.

5. Ignition ON, after 30 seconds verify that a test lamp illuminates between control circuit terminal A8 and B+.
6. Ignition OFF, verify that a test lamp does not illuminate between control circuit terminal A8 and B+.

• If the test lamp illuminates, test the control circuit terminal A8 for a short to ground. If the circuit tests normal replace the HVAC control module.

7. Ignition ON, after 30 seconds verify that a test lamp illuminates between control circuit terminal A7 and B+.

• If the test lamp does not illuminate, test the control circuit terminal A7 for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.

8. Ignition OFF, verify that the test lamp does not illuminate between control circuit terminal A7 and B+.

• If the test lamp illuminates, test the control circuit terminal A7 for a short to ground. If the circuit tests normal replace the HVAC control module.

9. If all circuits test normal, replace the air temperature actuator.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Control Module References
* Air Temperature Actuator Replacement

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