Instrument Lighting
Instrument Lighting
The instrument lighting lights up the instrument cluster and the operating switch.
Brief description of components
Light switch
The light switch consists of
- Rotary switch for sidelights and low beam (and special equipment Automatic Light Control)
- Two buttons for fog lights and rear fog light
- Potentiometer for dimmer of panel illumination
- Potentiometer for manual headlight beam height control in the case of halogen headlights
Power supply: The switch is supplied with 5 Volts by the light module.
If the power supply is defective, the light remains ON: the light is automatically switched on if
- the cables to and from the light switch have been cut or
- are switched to ground
- are at 12 V.
- For safety reasons, the light switch can only be switched OFF if there is 5 V at both switch outputs to the light module. If a short circuit means that there is once 5 V and once 12 V, the light can not be switched OFF: low beam and Automatic Light Control remain ON.
Light module
The light module controls and monitors the vehicle lights. Information is received and sent via the data bus K-CAN SYSTEM.
In the case of the special equipment xenon headlights, the defects of the xenon headlights are evaluated in the light module.
Emergency operation properties of the light module: The light module is supplied with terminal 30 twice.
If a terminal 30 fails, the following are activated:
- Front lighting: low beam and parking light (each on one side).
- Tail lighting: On one side, the outer sidelights/brake lights are activated. On the other side, the inner taillights are activated. The vehicle thus still has lights on both sides. Confusion with a one-track vehicle (motorcycle) is excluded.
- Brake light: One side of the brake lights is activated with normal power (ECE coding). This leads to "one-track" braking, as if for example one brake light had failed.
In the case of a failure of the processor, emergency operating mode is activated. Emergency operating mode involves hardware that is completely independent of the light module. Emergency operation properties with failure of the processor:
- Vehicle lighting: At terminal 15 On, the following are switched on: Front low beam and outer rear sidelights/brake lights left and right. The outer sidelights/brake lights left and right are not, as would be normal, dimmed to 10% of their brightness, but operated with full power. This ensures the function of the vehicle lighting irrespective of the position of the light switch.
- Brake light: With terminal 15 On, the left and right brake lights are switched on when the brake light switch is operated (via a hardwired, direct line from the brake light switch to the lamp drivers).
Function defects with failure of the processor:
- No turn indicators and hazard warning lights, no high beam, no headlight flasher, no fog lights, no rear fog light, no third brake light
- No communication across the K-CAN SYSTEM.
- No communication with the trailer module
Main functions
Brightness control of the instrument lighting
The light module supplies the voltage for the instrument lighting.
Dependent on the following factors:
- the potentiometer setting in the light switch
- the basic brightness measured in the instrument cluster.
The data exchange from the instrument cluster to the light module is via the K-CAN
The output on the light module for terminal 58g is short-circuit proof.
The output voltage is pulse-width modulated.