Design

Design

Headlights





Warning! The ballast, which is located in the wheel arch liner, and the wiring for the Bi-Xenon lamps are high voltage.

The headlights are operated via the light switch module (LSM). This is on the dashboard at the side of the steering wheel. The light switch module (LSM) is directly connected to the central electronic module (CEM). Low and high beam are operated by moving the left control stalk toward the steering wheel.
In the Bi-Xenon lamps, an actuator motor (solenoid) is used to move a cover in front of the lamp in the lamp housing in order to switch between high and low beam.
In cars with Bi-Xenon lamps, the lamps are powered directly via the central electronic module (CEM) without pulse width modulation.
To detect problems with the low beam, the central electronic module (CEM) reads the power consumption of the circuit. If this falls below a certain threshold value a fault will be indicated. The general warning lamp lights in the driver information module (DIM) and a text message is displayed.
Lighting the headlight
It normally takes 3 seconds from activation at the light switch with the ignition on to the lamp lighting.
- As with normal headlights, the lamps remain off while the starter motor is cranking and come on once the engine is running.
- On each occasion that voltage is supplied to the ballast 3 attempts, within 1 second, are made to light the lamp.

Right and left-hand asymmetric lamps




The right and left-hand asymmetric lamps are adjusted mechanically using a simple operation. A lever is accessible when the rear cover on the headlight housing is opened.
A = left-hand asymmetric lamp
B = right-hand asymmetric lamp

Automatic headlight levelling




Motors integrated in the headlights regulate the beam range of the headlights.
The motors adjust the headlights vertically depending on load and road conditions to reduce the risk of dazzle.
The motors are regulated via signals from one position sensor at the rear axle and one at the front axle.
The position sensor are directly connected to the "master" gas discharge lamp module (GDL). The sensors detect vehicle angle in different load conditions and transmit information to the "master" gas discharge lamp module (GDL), which then sends control signals to the motors regulating beam range.
If there is a fault in the automatic headlight levelling for the Bi-Xenon lamps, the actuator motors will automatically set the beam range to the shortest level.
There are diagnostics for the headlight levelling.

Headlight levelling position sensors (Bi-Xenon)




Cars with Bi-Xenon lamps have two position sensors so that the headlights can be adjusted automatically. Vertical adjustment accounts for load and road conditions to reduce the risk of dazzle.
One position sensor is located next to the rear axle and is connected to the left rear control arm via a link system. The other position sensor is located next to the right front axle and is connected to the right front control arm via a link system.
Vehicle angle is measured by the sensors being actuated via the respective link system.
The position sensors are directly connected to the "master" gas discharge lamp module. The signals are received by the "master" control module. If speed is above 5 km/h (3 mph), an average value is calculated. The processed information is sent to the "slave" gas discharge lamp module (GDL) via LIN communication.
The position sensors are calibrated using VIDA. The calibration is saved in the "master" control module. The calibration needs to be repeated if the control module or a position sensor has been replaced.

Calibration

Caution! Position sensor calibration is required after work such as sensor removal/installation, or replacement of a sensor, the control module, rear axle, front axle, bushings, shock absorber or springs.

Calibrate as per the tab DIAGNOSTICS/VEHICLE COMMUNICATION/Central electronic module (CEM).
Calibration must always be performed with the vehicle unlocked and stationary on a level surface.
There are diagnostics for the position sensors.
Beam adjustment is carried out conventionally (via adjustment screws by the headlight).
For more information on beam adjustment, see REPAIR AND CLEANING, CONTROL AND ADJUSTMENT, Group 3, Front lighting, Headlight setting.

Safety
- In the event of a short-circuit on the high tension side the power supply cuts in less than 10 ms
- If the high voltage circuit is broken (such as due to an open circuit, defective bulb or no bulb in the lamp socket), during each activation the system attempts to light the lamp for a period of 700 ms. During the period, there is high voltage across the ballast.
- Approximate temperatures of components during operation: Ballast = 130 °C (265 °F), Bulb holder = 170 °C (340 °F), Bulb = 400 °C (750 °F).
- The glass body of the Bi-Xenon-lamp is filled with different gases and metal vapors which are under pressure. The lamp can explode as it is under gas pressure.

Warning! Follow the safety instructions and recommendations in VIDA carefully when working with high voltage.Use safety goggles when handling the bulb. Risk of explosion!The electrical system must be switched off before starting work.Risk of burn injury. The components operate at very high temperatures.

High voltage unit




- High voltage is required to light the Bi-Xenon lamp.
- A high voltage unit is connected to each Bi-Xenon lamp. This transforms 12-V voltage to the approximately 24,000 V required to light the lamp. Once the lamp is on, voltage is lowered to the approximately 100 V required to keep the lamp lit.
- Each time voltage is supplied to the high voltage unit, an attempt is made to light the Bi-Xenon lamp. If this voltage does not exceed 9.5 V during a time period of 200 ms, the lamp does not light. If voltage is too low, such as after a voltage-consuming cold start, the lamp does not light just because the engine is running and the alternator begins charging. A new attempt must be made to start the lamp by turning the light switch to the "0" or parking light position and then back to the low beam position.

Warning! Because of the high voltage it is important to follow the instructions for working with Bi- Xenon lamps and the high voltage unit!