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Another buld alert issue...


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Previously I had an '08 12RT that I added a tag bracket with an LED tail/brake light combination. Wired it into the stock tail light assembly & had no issues.


Now that I have the '07 GS/A, I've wired the exact same unit exactly the same as before. But now I'm getting the dreaded lamp alert on the display with the glaring yellow triangle. I've dAAAble checked & triple checked with friends, & all bulbs & LED lights work as they should.


What the hey? Is there a difference in wiring or CanBus from '07 & '08? I've asked some reasonably smart guys, & we're stumped.

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Your problem isn't with the CAN bus, it's with the Central Chassis Electronics (ZFE). The CAN bus simply transfers digital data words from one control unit to another. The ZFE is the unit responsible for controlling your bike's electrics.


There is a difference in the wiring between your old RT and your current GS. Your old RT had two single-filament rear lamps, wired in parallel. The lamps received a pulsed 12-volt signal when acting as tail lamps, and a steady 12-volt signal when the brakes were applied, resulting in increased brightness. Your GS has one dual-filament rear lamp. The low power filament is the tail lamp. and the high power filament is the brake lamp. Apparently this change in wiring is causing the ZFE in your GS to flag the current to the tail lamp as too low and give you the lamp warning.

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Evening Danny


First off, the rear lighting is not "on" or controlled by the Can (CanBus) system. The only part of that system that is on the Can is the ABS/ZFE controller reporting the light out to the dash controller.


As far as rear lighting differences between the 08RT & the 07 GS-A? --Yes


The 08RT used a single filament bulb(s) that were pulse width modulated by the ZFE controller to pulse the bulb at a little over 1/2 voltage for tail light & full 12v+ for brake light.


You will have to look at yours to be sure but about that era GS-A used a double filament rear bulb with a separate tail light (5 watt) & something like a 21 watt brake light (in same bulb). Not sure on the 07 & I'm a long ways from my wiring schematics this week. Some also used an L.E.D. rear light set up but still separate tail/brake light circuits.


If you can determine what you have back there as far as bulbs or LED & if you determine it is a twin input (one wire for brake & one wire for tail (common ground) then maybe we can help you wire your additional light correctly.


I only check in here infrequently the rest of this week so if you don't hear back from me I'm not ignoring you I'm just off the grid for a while this week.



Added: is the rear light you are adding a single or dual input light?


Added 2: It looks like Karl was posting while I was typing but we said about the same thing.

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Thanks Karl & DR. As I recall, when I wired this to my '08 RT, I had of course the ground going to brown, & the two separate wires each going to tail & brake lights. It was different on the GS/A. I ended up with both hot wires from the LED bracket going to the same wire that activates the tail & brake light. The auxiliary LED has the tail light as normal & the brake light works as normal as well.

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Evening Danny


That 08 1200RT should have had only one wire feeding both rear bulbs (single filament bulbs) & that wire was pulsed for tail & on steady for brake light.


Your GS-A should have twin filament bulb (or LED array) with a brown ground wire & GRAY/RED/YELLOW wire & a GRAY/BLACK/YELLOW wire.


The brown is ground, I can't remember which is which but one the other wires is BRAKE light & one is TAIL light.


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Brown is indeed ground. Been that way since my /5 days. There are two wires going to tail & brake light even though it's a single dual filiment bulb. But for some reason I had to wire the auxiliary to one wire, otherwise I had a constant brake light on the LED.

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There are two wires going to tail & brake light even though it's a single dual filiment bulb. But for some reason I had to wire the auxiliary to one wire, otherwise I had a constant brake light on the LED.


Evening Danny


That sounds like might have wired you AUX BRAKE light input to the GS-A's tail light wire. (just a quick guess on my part)


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I'm pretty sure it's a fault on my part, & nothing to do with the bike. It's happened before.


Where's my NASA electronics technician Dad when I need him? :P

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