LED Rear tail and break light

[stuckinmud]

I broke the tail light lens on my 05 R1200GS and figured this would be a good time to update to a clear lens. After allot of research I decided to go with a LED arrangement as well. The XForce LED Tail Lamp. 254-506 Clear with 12 LEDs looked like a good solution. Purchased from a Ebay store. The LED light arrived from the UK in good order in a nice box. Total with shipping was around $75. It's a sealed unit and feels as though it uses much thicker plastic than the stock red lens. Note that the 05 to 07 R1200GS bikes use a std 1157 type light bulb and draw significantly more current than the LED setup. The bikes CAN bus system detects this and will indicate a tail light fault and if the current goes low enough will turn on the break light. I've read that the BMW dealer may be able to change the setting in the bikes computer to correct this problem and act like a newer bike that comes std with LED tail lights.

Here are some measurements I took to determine how to resolve this fault.
1157 bulb tail .6 amps, break 2.1 amps.
XForce LED Tail Lamp. 254-506 Clear, 12 LEDs. Tail 30ma, 148ma break. Tail light circuit draws no current when the break is on.

Bike turns on break circuit when no current is drawn from the tail light.
No additional current drop is required on the break circuit.
Tail light circuit: 150 ohm resistor did not meet the bikes requirement when the break was applied.
100 ohm resistor met the current requirements satisfying the fault detection. 14V / 100 = .140 amps. .140 amp X 14 = 1.96 Watts.

I ended up connecting two 220 ohm 2 Watt resistor in parallel across the tail light wire and ground. It looks great and works great.

[gdayjr]

I bought a similar light from an online dealer in china, and could not get it to work.
I could have tail lights or brake lights but not both. I am not technical enough to figure out why, so i might try your solution and see if it works.

Delivered to Australia from China, $29 Aus

[MPFITZ]

Thanks for posting your solution!!!

I have an 07 and just yesterday was at the dealer asking if we could "retro fit" a LED tail light from the new 2011 models that looks cooler and is I'm sure significantly brighter. One of the dealer techs said he was trying to do the same thing on his 07 GS but as of yet could not figure out the electrical "resistor" solution.

I am going to call him on Monday and show him your post. If that does the trick, KUDOS to you for your ingenuity

Thanks again!

[marc]

Be aware that the rear brake and taillight circuit works in one of two methods. Alas, I don't know of any way to tell which method is used on some bikes without dragging a O-scope out to the bike.

Method 1: the brake and tail lights are separate. If there isn't an appropriate current draw the system will throw a LAMP fault. The resistor solution for LED lights will work if your bike uses this method.

Method two: the brake and tail lights work together, with the bike using pulsw width modulation (PWM) to vary the effective voltage. Full voltage on both circuits are used for brakes, partial effective voltage on both circuits are used for the tail light function. I suspect that the resistor solution will not help if your bike uses this method, but I'm not 100% sure about that.

I'd guess that the newer bikes, say 2007 and later, use method two. LED lights made for use with that system will not work on a bike that uses method 1 regardless of resistors.

[stuckinmud]

Originally Posted by MPFITZ

One of the dealer techs said he was trying to do the same thing on his 07 GS but as of yet could not figure out the electrical "resistor" solution.

I am going to call him on Monday and show him your post.

Sounds good. Also please ask him to check and see if the bikes computer can be adjusted for the current change.

[stuckinmud]

Originally Posted by marc

Be aware that the rear brake and taillight circuit works in one of two methods. Alas, I don't know of any way to tell which method is used on some bikes without dragging a O-scope out to the bike.

Interesting. I'll look into this more and get back to the forum. I did my testing with a DVM and saw some oddities you would not see in an Analog circuit. When I get some time I'll put a scope on it. I also have access to 07 and 09 GS's as well.

[stuckinmud]

I verified the 05 through 07 use the normal method of turning the tail light and break light elements on separately. I this case the resistor method will work fine. Here is a photo of the end result with clear lenses on the turn signals as well.

[CaptStevens]

Originally Posted by stuckinmud

I verified the 05 through 07 use the normal method of turning the tail light and break light elements on separately. I this case the resistor method will work fine. Here is a photo of the end result with clear lenses on the turn signals as well.

Not to change the subject, but what brand of panniers do you have on your bike? I am in a quandry as to which to buy for my 2012 R1200GS!!
I don't want to spend a ton of money (The BMW adventure bags are Outrageous)!!!

[RickC]

Capt., I think those are the standard adventure bags