Gas discharge headlamps are available as an option, the dip beam is produced by a 35 Watt gas discharge lamp. The gas discharge lamp delivers three times as much light intensity as a conventional H7 bulb.
The headlamp consists of the following components:
- Headlamp housing
- Headlamp housing cover
- Gas discharge lamp for dipped and main beam
- Halogen bulbs for main beam and headlamp flasher
- Bulb - indicator
- Bulb - parking lamp
- Headlamp range control motor
- Starter
- Electronic control unit
Operation
WARNING:Voltages of up to 30 kV are possible.
Similar to sunlight, the light produced contains a high proportion of green and blue.
Owing to the special construction of the bezel and lens, the range is greatly improved and the close-up spread is wider. This results in better illumination of the edge of the road, without exceeding the limiting value for dazzle.
A further advantage of the chosen light distribution is a softer transition at the light - dark boundary. A light - dark contrast which is too high can lead to disturbing changes in the road illumination when driving. Gas discharge headlamps make a decisive contribution to improvements in active safety.
Full light intensity from a gas discharge headlamp is first reached one minute after switching on. For use in motor vehicles, special electronic equipment is therefore necessary to ensure immediate effect.
The glass bulb of a gas discharge lamp is filled with Xenon gas and a mixture of metal halide salts.
A brief high voltage of 20 kV ignites the gas between the two electrodes. After a short overcurrent phase, during which the light arc stabilises, the lamp power is regulated by the electronics to 35 Watts.
The wear on the lamp is so low that the life of a gas discharge bulb is for the whole life of the vehicle.
The side lamps and the indicators are integral with the headlamp housing.
Headlamp levelling - gas discharge headlamp
An automatic headlamp levelling system is required by law on vehicles with gas discharge headlamps.
The system consists of the following components:
- Vehicle level sensors on the front and rear axles
- Master control module on the left-hand headlamp housing
- Slave control module on the right-hand headlamp housing
- Headlamp levelling motors in both headlamp housings
In order not to dazzle oncoming traffic, the adjustment is made depending on the vehicle loading as soon as the ignition is switched on.
No adjustment of the range takes place during dynamic processes (braking, accelerating, pulling away).
NOTE:After work is done on the headlamp levelling sensors, the headlamp levelling system must be re-calibrated and initialised using WDS.
The vehicle height sensors on the front and rear axles send a load dependent signal to the master control module. Based on the difference between the two signals, the module calculates the optimal angle of the light bundle and sends the necessary data to the slave module. Both modules generate control signals from the actual and desired positions of the headlamp reflectors for the headlamp levelling motors.
When the dipped beam is switched on, the system compares the actual load state with the original setting. In this way, illumination of the road is reduced and dazzling the oncoming traffic is prevented.
Headlamp levelling system - conventional headlamps
NOTE:The basic alignment of the headlamps must always be carried out with the headlamp levelling switch in position 0.
Each headlamp has an actuator motor which can be operated through the switch. The motor moves a pivoting headlamp reflector to the desired position using an adjusting spindle.
The headlamp levelling switch has two settings. In setting 0 the switch clicks in, this is the base setting. In position 4 the headlamps are inclined at their maximum angle.
The headlamp levelling system is operated by DC motors. The voltage is set through a potentiometer integral with the headlamp levelling switch (required value). Using the same principle, the actuator in the motor produces a voltage dependent on the position of the adjusting spindle.
The required value (switch setting) and the actual value (adjusting spindle) are compared. Depending on the voltage difference, the reflector is moved upwards or downwards until the voltages are identical.
For reasons of safety, the system is set to dipped beam if the signal is missing or is faulty.
Headlamp washer system
A headlamp washing system is required by law on vehicles with gas discharge headlamps. This consists of a high-pressure wash system.
The inactive nozzle holder is located in the bumper.
With the headlamps on, as soon as the front windscreen washers are operated, the telescopic nozzle holder is extended and cleans the headlamp outer surface (plastic covering lens) using a high-pressure jet.
An additional high-pressure pump is mounted on the washer fluid reservoir for the high-pressure washing system.
The daytime running lamps which are a reduced intensity dipped beam, must come on when the ignition is switched on. The daytime running lamps consist of:
The reduction in the voltage at the dipped beam bulbs is achieved by series connection of the dipped beam bulbs or by a pre-resistor, the reduced intensity dipped beam resistor. The intensity of the dipped beam is reduced in this way.
If the side or headlamps are switched on at the light switch, the daytime running lamps relay pulls in, and breaks the circuit through the reduced intensity dipped beam resistor. If the light switch is in the "Headlamp" position, the dipped beam bulbs receive their voltage through the dipped beam relay and light with full intensity.
The diodes for the daytime running lamps only allow the current to flow in one direction when the light switch is switched on, as otherwise a few contacts in the light switch which are not required for the daytime running lamps would be made.
Procedure if there is a concern over the formation of condensation inside the plastic headlamp lens or if the plastic headlamp lens is split.
