Car heater resistor

How to detect the passenger compartment fan speed regulator failure

The fan speed regulator should be tested as follows. You have to dismantle the part, and connect the wires going to it directly with each other, using a jumper. If, after doing this, the fan turns on, the tested component is defective. Besides, installing a known good part in the place of the tested regulator will help to identify the failure of the latter.

If you have a multimeter, you can check the component serviceability by measuring resistance. The obtained results should be compared to nominal values that are usually specified in the car technical documents.

You may identify that the passenger compartment fan speed regulator requires to be checked, by the following symptoms:

• the fan operates erratically;
• it only works at the maximum speed;
• the fan activates even when the ignition is turned off;
• the electric motor speed is now falling, now rising;
• after a night parking, the vehicle battery is completely discharged.

Causes of the passenger compartment fan speed regulator failure

Most often, the regulator malfunction is caused by the impact of high temperature. Overheating often results from the fan operation at low revs, delayed cabin filter replacement, and hot weather.

In some cases, the regulator burnout is caused by jamming of the fan impeller.

Moisture and dirt produce disruptive impact on the contacts of the printed circuit board of the regulator. The risk of the regulator components corrosion considerably increases if the housing integrity has been impaired due to mechanical damage. In addition, temperature changes contribute to water condensation inside the regulator. The part failure may as well result from rusting of the motor shaft.

The part fasteners can be loosened due to increased vibration, which leads to unreliable fastening of the connector and the terminal block.

Replacement of the passenger compartment fan speed regulator

The fan speed regulator is not repairable. When a fault occurs, the part is replaced. The replacement procedure is quite time consuming, but you can carry it out on your own. For this you will need to adhere to the following procedure:

1. Remove the glove box, after unscrewing the fasteners, disconnecting the retaining strap and removing the damper.
2. Dismantle the hands-free system if it is installed.
3. Dismantle the glove box bottom casing together with the light.
4. Disconnect the servo drive for the EGR system right flap.
5. Unfasten the flap bracket fasteners and remove it.
6. Remove the wire harness connector from the regulator housing.
7. Unscrew the self-tapping fastening screws of the regulator, and dismantle the part. After that, mount a new one in its place.

Sometimes you need to remove the cabin filter and the fan to dismantle the regulator. Before proceeding with the replacement, see the sequence of steps in the vehicle technical documents.