Headlamp control, function

S82.10-4722-79

S82.10-4721-79

Function requirements, driving lights actuation, general

 No overvoltage or undervoltage

Driving lights actuation, general

Driving lights actuation includes all functions which serve the optimum illumination of the road while driving.

The driving lights actuation encompasses the following subfunctions:

 Function sequence for low beam actuation

 Function sequence for high beam actuation

 Function sequence for daytime running lights actuation

 Function sequence for auto on/off driving lights

 Function sequence for headlamp range adjustment (HRA [LWR])

 The light switch sends the circuit status "circuit 15 ON" to the fuse and relay module control unit (SRM).

Additional function requirements for low beams actuation

 Circuit 15 ON (ignition ON)

Function sequence for low beam actuation

Halogen lamp unit (code L12 (headlamp, halogen))

The central gateway (CGW) reads in the status of the light switch and sends a request to switch on the low beams to the fuse and relay module control unit (SRM).

The fuse and relay module (SRM) control unit controls the following lamps:

 Via the left front lamp unit, the left low beams

 Via the right front lamp unit, the right low beams

 Via the left rear lamp unit, the left tailgait, brake, and parking turn signal lights

 Via the right rear lamp unit, the right tailgait, brake, and parking turn signal lights

The SAM control unit also sends the request "request "Low beams indicator lamp" to the instrument cluster (IC) control unit, which then actuates the low beams indicator lamp.

LED lamp unit (code LG7 (LED High Performance headlamp))

The SAM control unit reads in the status of the light and sends a request to switch on the low beams to the fuse and relay module control unit (SRM).

The fuse and relay module (SRM) control unit controls the following lamps:

 Via the left front LED lamp unit, which then actuates the left low beam (short range) and left low beam (long range).

 Via the right front LED lamp unit, which then actuates the right low beam (short range) and right low beam (long range).

 Via the left rear LED lamp unit, the left LED taillight

 Via the right rear LED lamp unit, the right LED taillight

The SAM control unit also sends the request "request "Low beams indicator lamp" to the instrument cluster (IC) control unit, which then actuates the low beams indicator lamp.

Additional function requirements for high beam actuation

 For high beam function: circuit 15 ON (ignition ON) and low beams ON

 For headlamp flasher function: circuit 15 R ON

Function sequence for high beam actuation

The high beams actuation is comprised of the following subfunctions:

 Function sequence for high beams

 Function sequence for headlamp flasher

Function sequence for high beams

High beam actuation is requested by pushing the combination switch forward.

The steering column tube module control unit (MRM) reads in the switch position of the combination switch directly and sends it to the SAM control unit.

The SAM control unit sends the request "high beams ON" to the fuse and relay module (SRM) via a direct line. This then actuates the left and right high beams.

The SAM control unit also sends the request "request "High beams indicator lamp" to the instrument cluster (IC) control unit, which then actuates the high beams indicator lamp.

Function sequence for headlamp flasher

The function sequence and signal path for the headlamp flasher function correspond to that of the high beam function. However, to request the headlamp flasher function, the combination switch must be pulled backward. If the combination switch is pulled back and held, the high beam actuation remains active.

Additional function requirements for daytime running lights actuation

 "Engine running" signal set.

 Illumination switch in "AUTO" position

Function sequence for daytime running lights actuation

LED lamp unit (code LG7 (LED High Performance headlamp))

The SAm control unit reads in the status of the light switch directly and sends a request to turn on the left and right parking/standing/daytime running lights to the fuse and relay module control unit (SRM).

The CDI or ME-SFI control unit sends the signal "engine running" to the SAM control unit. In addition, the CDI control unit or ME-SFI control unit sends the vehicle speed to the SAM control unit.

 Depending on the vehicle speed, the SAM control unit activates the parking/standing/daytime running light function.

Additional function requirements for auto on/off driving lights

 "Engine running" signal set.

 Illumination switch in "AUTO" position

Function sequence for auto on/off driving lights

The auto on/off driving light function controls the following functions:

 Standing/parking/daytime running lights

 Low beams (short range)

 Taillamp

 License plate lamp

The SAM control unit reads in the status of the light switch directly and sends a request to switch on the auto on/off driving lights to the fuse and relay module control unit (SRM).

The humidity sensor/light sensor/rain sensor or humidity sensor/light sensor/rain sensor/sun sensor sends its information for the ambient brightness (twilight level) to the SAM control unit, which activates or deactivates the auto on/off driving light function via the fuse and relay module control unit (SRM).

 In the auto on/off driving lights, the low beams are automatically switched on or off.

 The low beams are switched on or off depending on the ambient brightness (twilight level).

The atuo on/off driving lights function comprises the following partial functions:

 Function sequence for auto on/off driving lights over light sensor

 Function sequence for auto on/off driving lights over wiper activities

Function sequence for auto on/off driving lights over light sensor

 Depending on equipment installed, different light sensors are installed: humidity sensor/light sensor/rain sensor (B38/2) (with semi-automatically controlled air conditioning, TEMPMATIC) or humidity sensor/light sensor/rain sensor/sun sensor (B38/3) (with THERMOTRONIC automatic climate control).

The ambient brightness (twilight level) is detected by the humidity sensor/light sensor/rain sensor or humidity sensor/light sensor/rain sensor/sun sensor. This sends a signal to the SAM control unit, which activates or deactivates the high beam function via the fuse and relay module control unit (SRM).

 If the humidity sensor/light sensor/rain sensor or the humidity sensor/light sensor/rain sensor/sun sensor fails, the auto on/off driving lights are not deactivated until the engine is switched off.

Additional function requirements for auto on/off driving lights over wiper activities

 Circuit 15 ON (ignition ON)

 Illumination switch in "AUTO" position

Function sequence for auto on/off driving lights over wiper activities

If the windshield wiper system is activated and from 4 wiping cycles, the SAM control unit activates low beams actuation. If the windshield wiper system is shut off, low beams actuation is deactivated.

Additional function requirement for headlamp range adjustment (HRA)

 Driving lights ON (low beam or high beam)

Function sequence for headlamp range adjustment (HRA [LWR])

The automatic HRA [LWR] corrects the headlamp range of the vehicle headlamps in accordance with the load and the vehicle pitch motions caused by the vehicle dynamics.

The left headlamp range adjustment actuator motor and right headlamp range adjustment actuator motor reads in the signals from the rear axle directly and evaluates them.

In vehicles without automatic HRA, the headlamp range of the vehicle headlamps is controlled by the headlamp range controller (S1s8).