Headlamp: Description and Operation

General Information

The headlight automatic vertical aim control system keeps the low beams at a constant level even when the vehicles inclination has changed due to changes in load.

There are two level sensors, one on the front axle and one on the rear, which detect the vehicle's level of inclination. In addition, the vehicle speed signal is also used.

The control module evaluates these signals and activates the automatic headlight beam adjusting motors, when the headlights are switched on.

Headlight automatic vertical aim control is required on vehicles equipped with high intensity gas discharge (Xenon) headlights.

Function
The headlight automatic vertical aim control system consists of:
- Automatic vertical headlight aim control system control module -J431-
- Left rear level control system sensor -G76-
- Left front level control system sensor -G78-
- Left headlight beam adjusting motor -V48-
- Right headlight beam adjusting motor -V49-

When the engine is started, a nominal value is created depending on the actual inclination of the vehicle. This value is sent to the headlight beam adjusting motors, and the headlight beam angle is adjusted once, whether the low beam is switched on or not.

After this initial adjustment, signals to change the low beam position will only be sent to the headlight beam adjusting motors if the low beam headlights are switched on.

If a trip is interrupted (vehicle speed less than 1 km/h) and a change in the vehicle inclination is recognized (i.e. additional passenger(s)), the headlights will automatically adjust to compensate for the increased load.

All control processes for the headlight automatic vertical aim control originate from static operating conditions.

NOTE: The following information relates solely to the VAG1551 scan tool.