Car headlight leveling motor

How to detect the headlight adjustment stepper motor failure

Diagnostics of the headlight adjustment stepper motor can be easily performed on your own. The inspection method is selected depending on the failure nature. If, when switching on the ignition and trying to adjust the headlights, you do not hear the specific buzz, check the supply circuit for integrity. For this, you have to disconnect the wire harness from the component and fix the test probes on its terminals. Then you should switch on the ignition and check the voltage between the appropriate terminals, adjusting the headlights position with the switch situated in the cabin. If a break in the adjuster power supply circuit is not discovered, the component requires replacement.

If the buzzing is heard when you switch on the adjuster, but the light is not adjusted, the teeth of the rod or gear may have been scuffed. But the problem can be not only in the electric motor, but in the jammed headlight reflector.

If the headlight adjuster is operating erratically, you need to disassemble the electric motor. Contact oxidation, wear of graphite tracks, gear teeth and rod indicate that the part requires replacement.

You may identify that the headlight adjustment stepper motor needs to be inspected by the following symptoms:

• the electric motor does not switch on;
• the headlight adjustment mechanism works erratically;
• the light adjustment is too slow;
• while driving a knocking sound is heard in the area of the headlight;
• the motor continues working even after the adjuster is turned off.

Causes of the headlight adjustment stepper motor failure

Often the headlight adjustment stepper motor faults result from abrasion of the plastic gear  teeth or burrs on the adjustment screw. Insufficient engagement of the worm gear components leads to faults in the adjuster operation. Premature wear of components can occur due to a lack of lubricant, its contamination or ingress of foreign objects into the housing.

As a consequence of exposure to dirt and moisture, the circuit board contacts can oxidize or wires can break. Besides, the insulating layer of the motor winding becomes disrupted, which results in its short-circuit.

Driving on poor quality roads, increased vibrations in the engine compartment, improper attachment of the component during installation often promotes loosening of the fastening elements inside the motor, which causes slipping of the worm gear.

Sometimes the headlight adjuster malfunction results from the broken ball end of the rod inserted into the reflector groove. In such a case, the electric motor is operating, its rod is moving, but headlights are not being adjusted.

Repair and replacement of the headlight adjustment stepper motor

To restore the component performance try cleaning the connector and socket from oxide and dirt, align the bent contacts. If it does not help, replace the component.

You can install a new motor on your own. For this disconnect the power supply wire harness, turn the adjuster by 45° clockwise or counterclockwise and remove it.

On some cars you have to remove the expansion tank, the air filter, and sometimes headlights to open access to the part. Before you start the replacement, specify the procedure in the car technical instructions or contact specialists for assistance.