NOTE: Test numbers refer to numbers on diagnostic chart.

This step checks to see if improper temperature regulation is due to air mix door movement.
This step checks to see if improper temperature regulation is due to poor aspirator airflow. To check aspirator airflow, start engine. Vehicle must NOT be in direct sunlight. Select "HI" blower speed and any mode except "DEF". Hold a 1" X 3" paper strip at one end, with the opposite end over the in-car temperature sensor inlet. Lower the paper strip until end is about 1/2" above the in-car temperature sensor inlet. If aspirator airflow is good, the end of the paper strip will be sucked against the inlet.
This step checks the accuracy of the in-car temperature sensor.
To adjust air mix door, lift straight up on the air mix door link to release it from the programmer arm. With the ignition on, select "Max Heat" and wait for the programmer arm to stop moving. Manually pull the air mix door link toward the passenger door until it hits the mechanical stop (air mix door in maximum heat position). With both the air mix door link and the programmer arm in the maximum heat position, snap the air mix door link back onto the programmer arm. Visually check the movement by selecting different temperature settings.
This step checks to see if binding or stopping is due to door or DC motor.

Fig 1: Chart 9, Improper Temperature Regulation

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Chart 9, Improper Temperature Regulation