Air Temperature Malfunction
Air Temperature Malfunction
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 and auxiliary is a 3-wire bi-directional electric motor. Ignition 3 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.
Circuit/System Verification
1. Ignition ON, engine running, place the blower motor switch at the maximum speed position and the mode switch in the vent or panel position.
2. Rotate the air 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 through the vent or panel positions.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the air temperature actuator.
2. Test for less than 1.0 ohm between the air temperature actuator ground circuit terminal 7 and ground.
^ If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify that a test lamp illuminates between the air temperature actuator ignition circuit terminal 10 and ground.
^ If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, replace the air temperature actuator.
4. Install a DMM between the control circuit terminal 8 and ground. Command the actuator in each direction. 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 the voltage does not change as specified, replace the HVAC control module.
5. If all circuits test normal, test or replace the air temperature actuator.
Component Testing
1. Install a 10-amp fused jumper wire between the control terminal 8 and 12 volts. Momentarily install a jumper wire between the control terminal 7 and ground. The air temperature actuator shaft should rotate.
^ If the function does not perform as specified, replace the air temperature actuator.
2. Install a 10-amp fused jumper wire between the control terminal 10 and 12 volts. Momentarily install a jumper wire between the control terminal 7 and ground. The air temperature actuator shaft should rotate.
^ If the function does not perform as specified, replace the air temperature actuator.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
* Recirculation Door Replacement.
* Refer to Programming and Relearning. Programming and Relearning