Light switch center (LSZ)

In addition to the electronic control and monitoring system for the external vehicle lights, the light switch center also comprises the switch for sidelights/low beam, the push buttons for fog lights and rear fog lights as well as the potentiometers for instrument locator lighting and manual headlight beam height control.

Scope of functions of light switching center

• Control and monitoring of the outer headlights and lamps, including the indicator and hazard warning flasher function
  
• Control of relay for fog lights
  
• Evaluation of load sensors for automatic headlight vertical aim control and the resulting activation of stepper motors of evaluation of potentiometer for manual headlight beam height control.
  
• Dimmer function for instrument and locator lighting (terminal 58g) as well as the function and locator lighting for the hazard warning switch.
  

Communication with other control modules and diagnosis takes place via the K-bus. The light switching center receives information via this bus relating to the vehicle status and also provides information on the status of the controlled lamps (defective/OK, switched ON/OFF).

The indicator lamps for high beam, fog light, rear fog light and direction indicators in the instrument cluster are controlled by the light switching center on the basis of K-bus telegrams.

Design

The light switch center consists of a control module and operating unit

Both units are interconnected by means of a plug connector.

Control module

The control electronics is accommodated in the control module.

Operating unit

The switches for sidelights/low beam, fog lights/rear fog lights as well as the dimmer for headlight beam height control and instrument lighting are integrated in the operating unit.

The operating unit can be replaced separately from the control module.

If replacement is necessary, corresponding reference to this is made in the test module.

Lamp monitoring

The lamps are monitored in OFF and ON status.

Cold monitoring in the OFF status takes place by briefly switching on the lamp (so short that the lamp does not light up). The lamp current is monitored and an assessment is made as to whether the lamp is defective or not.

Note

If the battery voltage drops below approx. 9.5 V, the lamp status can no longer be monitored or output.

Activating indicator lamps in the instrument cluster

The indicator lamps for left direction indicator, right direction indicator, rear fog lights, fog lights, high beam as well as the LEDs in the pictogram incorporated in the instrument cluster are activated via the K-bus.

Emergency mode

Independent hardware is provided in order to maintain the functions necessary for driving safety in the event of the control module failing.

If the light switching center is in emergency mode,

• Tail lights and low beam are switched on at terminal 15 irrespective of the position of the corresponding light switch
  
• Left and right brake lights are switched on at terminal 15 and the brake light switch operated
  
• Direction indicators, hazard warning lights, high beam, headlight flasher, fog lights and rear fog lights cannot be switched on.
  
• Diagnosis is not possible
  

If in emergency mode, the light switching center must be replaced.