Trailer lighting

The trailer lighting runs the following functions:

• Brake light
• Side lights/parking light
• Indicating, hazard warning flashers, crash alarm hazard warning flashers, DWA alarm flashing
• Rear fog light
• Reversing lights

The trailer module (AHM) activates the individual lighting circuits of the trailer. The implemented functions for the trailer lighting are described in the following section.

• Brake light 

  The brake light on the trailer is switched on when the service brake in the towing vehicle is operated.

• Side lights/parking light 

  The side lights on the trailer are activated when the light switch on the towing vehicle is in the side lights or low-beam headlight position. When the Automatic Light Control is activated, the side lights of the trailer are switched on depending on the level of brightness.

• Indicating, hazard warning flashers, crash alarm hazard warning flashers, DWA alarm flashing 

  The turn indicator has two flasher functions realized via the trailer module.

  • One-touch flashing:  When the turn signal/high beam switch is touched briefly, the turn indicator bulbs are activated briefly. The number of flashing pulses here depends on the encoding of the towing vehicle.
  • Continuous flashing:  When the turn signal/high beam switch is 'overpressed' beyond the pressure point, the turn indicator bulbs are activated with the function "continuous flashing".

    The flashing frequency is adapted to the flashing frequency of the towing vehicle by the trailer module (AHM). At the start of each flashing period, CAN messages are sent in cycles. These messages serve to synchronize the flashing frequency between the towing vehicle and trailer. If a turn indicator on the vehicle or the trailer is faulty, the flashing frequency will double.

• Rear fog light 

  The rear fog light is switched on with

  • terminal 15 ON and
  • the light switch of the towing vehicle in the low beam position
  • the rear fog light activated by the switch.

  Or with

  • terminal 15 ON and
  • the light switch of the towing vehicle in 'side lights' position and
  • the fog lights activated and
  • the rear fog light activated by the switch.

  The rear fog light is switched off again when

  • the rear fog light is deactivated by the switch
  • terminal 15 OFF, or
  • light switch OFF.
• Reversing lights 

The reversing light is switched on when reverse gear is engaged on the towing vehicle and terminal 15 is ON. The reversing lights are switched on with a delay of a fraction of a second to avoid their flashing during gear changes.