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Rear/Brake light wiring 2008 F650GS

5K views 14 replies 4 participants last post by  AWJDThumper 
#1 ·
I'm looking to wire in an additional brake light on a top box. But looking at the existing wiring to the rear light unit I can only see one live wire and an earth.
Baffled as to how one wire sends 2 signals, some kind of voltage/amperage boost for the brake light ??? (or am I perhaps suffering a senior moment)
There is an earlier thread re Givi topbox light but it relates to earlier model bike.
 
#7 ·
It looks as though the LED rear light option may well be CanBus controlled via a twisted pair harness. If so, you would need to navigate the complexities of how CanBus controllers work in order to be able to add the additional brake light:think:
 
#14 ·
The PWM simply causes the LED's to pulse in the same way with a higher duty cycle producing a brighter light - this is because the response time of the human eye only sees the average light level. However, you should see the effect of the pulsing using a digital camera?
 
#15 ·
I think I now understand the electrical system on the F650GS twin (and later F800GS etc) which is not straightforward because of its use of a CanBus network to simplify the wiring.

In terms of the rear lights and indicators, the CanBus itself is not used to control them as such. The F650GS twin uses a conventional harness with ~5 wires going to the back of the bike. Where LED lights are fitted (brake/tail or indicators), a pulse width modulated signal is employed to control the brightness - in the case of the lights, 100% duty cycle for the brake light and ~50% duty cycle for the tail light. That signal is generated by the Central Chassis Control Unit which can also be referred to as the CanBus Controller.

The complication in fitting an additional stop light is that the CanBus Controller monitors current use in order to sense faults and therefore the current use of the additional light needs to be taken into account. It's probably not that hard to sort out but is much more complicated than a system using incandescent light bulbs!
 
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