Headlamp Levelling

HEADLAMP LEVELLING

Headlamp levelling provides for the adjustment of the vertical aim of the headlamps. The levelling system is primarily required to minimise glare to other road users when a heavy load is in the rear of the vehicle.

Three systems of headlamp levelling are available; manual, static and dynamic.

Manual Headlamp Levelling
Manual headlamp levelling is only available on vehicles with halogen headlamps and coil spring suspension.

The manual system comprises the following components:
^ Two headlamp levelling motors
^ Headlamp levelling rheostat rotary control.

When the ignition switch is in the ignition position (II), power is supplied to the lighting control switch via the ignition relay in the battery junction box and to the headlamp levelling motor in each headlamp assembly via the CJB. When the lighting control rotary switch is moved to the side lamp or headlamp position, the supply from the ignition relay is passed to the levelling rotary control.

Movement of the levelling rotary control produces a variable voltage output, which is sensed by the motors. The motors react to the supplied voltage and move the headlamp to the requested position which relates to the supplied voltage from the levelling rotary control.

The headlamps can only be lowered from their unladen position to compensate for changes in vehicle attitude due to loading.

Vehicle Headlamp Levelling
Vehicle headlamp levelling is only available on vehicles with air suspension.

Vehicle headlamp levelling is performed by the air suspension system and the air suspension control module. The suspension system constantly monitors the vehicle attitude and adjusts the height of the front and/or rear of the vehicle accordingly. This maintains the correct vehicle attitude and consequently maintains the correct headlamp beam alignment.

The vehicle levelling system is fully automatic, therefore the lighting control switch does not have the manual levelling rotary control.

Dynamic Headlamp Levelling (Air Suspension)
Dynamic headlamp levelling is only available on vehicles with the AFS system and air suspension.

The dynamic headlamp levelling adjusts the vertical alignment of the headlamps as a rapid response to changes in vehicle attitude due to acceleration or braking.

The dynamic system is fully automatic, therefore the lighting control switch does not have the manual levelling rotary control.

NOTE: The AFS system also operates in conjunction with the vehicle levelling system as described previously.

The dynamic system comprises the following components:
^ Two headlamp levelling motors
^ AFS control module
^ Engine running signal from engine control module
^ Vehicle speed information from ABS module
^ Vehicle height information from air suspension control module.

When the ignition switch is in the ignition position (II), power is supplied to the lighting control switch via the ignition relay in the Battery Junction Box (BJB) and to the AFS control module. When the lighting control rotary switch is moved to the side lamp or headlamp position, the supply from the ignition relay is passed to the AFS control module.

NOTE: When the AFS control module receives an ignition on signal, the control module performs an initialisation procedure for both the AFS and headlamp levelling motors. Refer to the previous AFS section for details of the initialisation procedure.

The system operates by the AFS control module receiving inputs on the CAN from the air suspension control module for front and rear vehicle height, from the engine control module for engine running signal and from the ABS module for stop lamp switch active (brakes applied) and vehicle speed. The AFS control module processes these signals and provides an output to the headlamp levelling motors to adjust the headlamp vertical aim according to vehicle speed and attitude.

NOTE: In markets with Daytime Running Lamps (DRL), the dynamic headlamp levelling system will not operate when the DRL are active.