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Discussion Starter #1
OK you can-bus electrical guys, will this work?

I am going to change the single filament brake-taillight bulbs, on my 2007 R1200RT to LEDs.The OEM single filament bulb is higher in intensity when the brakes are applied, and there are two bulbs. There will be less current draw when I switch to LEDs.
I have a small single wheel trailer I am going to tow, it has a single bulb with two filaments for brake and taillight., I am going to use a single LED bulb there.

With less draw on the brake/taillight, will hooking the trailer bub, a LED, directly to the RT's taillight/brakelight wires, cause the computer to register a fault, over/under draw and shut the circuit down? If I try it can it hurt anything?

If I can make this work it is much simpler to wire, cheaper and I will have longer lasting LEDs bulbs on the RT and the trailer.

What do you think? Does this sound like a bright idea? ( I had to say that!)

Mick
 

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Mick - I'm not sure I'd bother to change out your taillight bulb to give you extra capacity for the trailer lights. LEDs draw such low amperage that I doubt your system would even register it. I wired in six-LED supplemental turn signal lights mounted underneath my mirrors and pointed more or less sideways to flash the bozos in my blind spots and there was no effect whatsoever on the performance of the turn signals, no error, no nuttin' except lots of bright amber light where I wanted it.

I also wired in 2x12 red LEDs (P3, Skene Design) as supplemental tail/brake lights, again no error message.

I think the problem you're going to have is interpreting the bikes two voltage tail/brake signal into the two filament bulb, irrespective of whether its LED or not. Taillight puts out ~4V to the bulb, brake ~12V. You may want to wire your trailer tail light to some other "switch on" 12V circuit (I used front running light) and tie the brake light into the existing tail/brake light circuit.

Skene Design may have a controller that would work for you - they sell the controllers separately from the light systems.

I've seen somewhere that if you do replace an incandescent with only LEDs you need to wire in a resistor into series in the circuit to "fool" the computer into thinking that there's a bulb there. Otherwise you get the "bulb out" error message.

JayJay
 

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Discussion Starter #3
JayJay said:
Mick - I'm not sure I'd bother to change out your taillight bulb to give you extra capacity for the trailer lights. LEDs draw such low amperage that I doubt your system would even register it. I wired in six-LED supplemental turn signal lights mounted underneath my mirrors and pointed more or less sideways to flash the bozos in my blind spots and there was no effect whatsoever on the performance of the turn signals, no error, no nuttin' except lots of bright amber light where I wanted it.

I also wired in 2x12 red LEDs (P3, Skene Design) as supplemental tail/brake lights, again no error message.

I think the problem you're going to have is interpreting the bikes two voltage tail/brake signal into the two filament bulb, irrespective of whether its LED or not. Taillight puts out ~4V to the bulb, brake ~12V. You may want to wire your trailer tail light to some other "switch on" 12V circuit (I used front running light) and tie the brake light into the existing tail/brake light circuit.

Skene Design may have a controller that would work for you - they sell the controllers separately from the light systems.

I've seen somewhere that if you do replace an incandescent with only LEDs you need to wire in a resistor into series in the circuit to "fool" the computer into thinking that there's a bulb there. Otherwise you get the "bulb out" error message.

JayJay

OK,

The bulb on the trailer has separate wires for the tail and brake. Your suggestion seems the easiest way to do it. It might work just using the wire for the brake light. I am going to try it in the morning and post the results. There are complete isolation relay harnesses available, but I am trying to be......frugal. Also I like a simpler solution, hopefully fewer wires and no relays.


Mick
MF
 

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Over the winter we purchased a Unigo and I ended up having to get two different electrical parts to get it to work. One was a 07660 Trailer Isolator, the other was a Trailer Relay Sub Harness for a BMW R1200RT 06 and above. Both items I purchased at www.electricalconnection.com, their phone number is 865-219-9192. I agree with the others that their is no need to change out the bulbs to LED.

Because of snow we haven't been able to take both the RT and Unigo out yet but it's getting better and will take it out on her maiden voyage soon.
 

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Discussion Starter #5
I ran jumpers from the tail/brake light wires at one of the light sockets of the RT, over to the trailer tail/brake light with the LED bulb. The taillight and the brake light LED worked with no fault registered. I guess I can do the directionals the same way. No isolation wiring harness needed. I just have to make up a simple wiring harness with a connector.

Mick
 

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You should always use an isolator to install the electrics to the trailer. The isolator uses a separate circuit from the bike to power the trailer. It uses trigger wires from the bikes lights to operate the trailer lights. This way if anything goes wrong with the trailer electrics it's not causing problems with the lighting circuit on the bike.
 

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It's your bike so do what you want but...uhh frugal?
do you have any idea how much BMW electrical components cost?
would you ride without insurance?
an isolator relay is nothing more than cheap insurance!
if nothing else at least put a fuse inline each wire.
 

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The RTP uses relays to work the extra police lights. You might try to find the relay unit, or just go to Radio Shaft and get a small 12V relay for a couple of bux.
 

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Discussion Starter #9
The isolation relay harness powers the trailer lights directly off the battery because with a controller area network system, too great a load will cause the computer to shut down that circuit. With a LED taillight the circuit is still not drawing enough to trigger a computer fault. If you burn out an incandescent bulb it will show up on the screen. If you have a short, the computer will shut that circuit down. The relay does draw some extra current, just not enough to trigger an over current. The LED bulb does the same thing.

Mick
 
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