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 side lights and low beam as well as Automatic Light Control (FLC) with light emitting diode FLC for driving light control
  
• Button for rear fog light
  
• Potentiometer for dimmer of panel illumination
  

The rotary switch for side lights and low beam has two switch contacts. Depending on the status of the two switch contacts, the light module can detect four switch positions:

S_SL = interior switch for side lights

S_AL = interior switch for low beam

1 = interior switch closed (after 5 V)

0 = interior switch open

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.

The faults 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 side lights/brake lights are activated (parking light). 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).
  

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 rear side lights / brake light lamps left and right. The side lights / brake light lamps 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 hard-wired, 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 rear fog light, no third brake light
  
• No communication across the K-CAN SYSTEM.
  

Main functions

Brightness control of the instrument lighting

The light module supplies the voltage for the instrument lighting. The voltage depends on

• the potentiometer position in the light switch and
  
• 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 shortcircuit-proof.

The output voltage is pulse-width modulated.