BMW Supplemental LED Brake Light Question

[rocketmanli]

I have a 2009 R1200RT. I'm trying to install the BMW Supplemental 16-LED Brake light without buying the BMW wiring harness. I have a FuzeBlock FZ1 drawing switched delayed-off power from the rear 12v accessory outlet.

I got the LED light wired up and installed a couple of days ago.
I ran the red wire from the light to a switched 12v (+) on my FuzeBlock FZ1.
I ran the black wire from the light to the (-) side of the FZ1.
I ran the gray wire from the light to a piggy-back spade connector on the (+) gray striped side of one of the brake light bulb sockets.
It lights.
Its so simple, there's no way to do it wrong.

Turning key on, LEDs light up as a running light.
Applying the brakes, LED light flickers for milliseconds, then goes solid. Like its supposed to.
Just seems to me there's very little difference in the intensity of the light from running light to solid brake light. If there is a difference, its barely noticeable.
If I unplug the gray trigger wire, and apply the brakes, obviously no flicker and no brake light; just running light.
If I unplug the gray wire, apply the brakes, then while applying the brake, plug in the gray wire, the intensity from off to on is definitely more visible. As in the difference in intensity is greater. Seems the brightness is correct with brakes applied, but it seems that in running light mode, its almost too bright.

The stock RT tail/brake light bulb is a dual filament bulb with 2 wires going to it. One black ground. And one gray striped hot. I'm told the CANBus sends 6-8 volts back there as a running light, and increases it to 12-14v when the brakes are applied.

Can't figure for the life of me, why I seem to be getting the full 12-14v for both tail light and brake light on the supplemental light. Seems I did the same connections I would have done with the harness, just without it.

I've spoken to 2 BMW techs and both said they've tried wiring the supplemental brake light the way I did, and it never worked properly. They said the CANBus is a strange system, and recommended I spring for the correct harness to get my light to work. That just doesn't make logical sense to me.

Any insight or advice would be appreciated.

 

[lkraus]

The stock RT tail/brake light bulb is a dual filament bulb with 2 wires going to it. One black ground. And one gray striped hot. I'm told the CANBus sends 6-8 volts back there as a running light, and increases it to 12-14v when the brakes are applied.

There are couple mis-statements here that are leading you astray, I think.

The RT rear bulbs are single filament (P21W or 1156). They receive a constant 12 volts when braking (full brightness). In tail light mode they receive a full 12 volts intermittently (AKA Pulse Width Modulation). The computer rapidly switches the bulb on and off to provide an average 6-8 volts to the bulb. The human eye averages out the pulses and perceives a dimmer light.

I suspect that your supplemental light is also pulsing along with the tail light voltage, but is not reacting as fast. So it is "on" longer than it is "off" and appears brighter than it should be.

 

[rocketmanli]

Great thoughts and thanks for the quick response, and the correction.
1. It would be great to hear from anyone here who has the supplemental light installed using the correct harness, and if they could tell me if there's a great difference, or slight between brake and tail light brightness.
2. Someone suggested installing a resistor in the red (+) LED light wire to reduce the volts when its in tail light mode. Do you think that would work, or do you think that would also lower the intensity of the LEDs in brake light mode as well? IF you think it would work, I've read that installing 2 equal size resistors of any size would cut the volts in half. Just not sure where or how to install the resistors.
Thanks again.
~me

 

[Paladinwest]

I bought four of the BMW lights two years ago to install on my 2008 R1200GSA, a friend's 2008 R1200GSA, a 2013 R1200GSA and a 2009 R1200RT. I got the correct harness for each bike (GSA's use one type and RT uses another). I did a test install on my bike before getting the others. The one that I used was the newer clear lens not the red lens model. I discovered that 1) the clear lens model does not flash, 2) there are two different clear lens models but they have the same part number and have different functions (on one there is no tail light, on the other has both tail and brake light). 3) the GSA harnesses were wired differently (again with the same part number). Of the ones that I installed my preference was the model with no tail light as there was more of a contrast when the brake was applied. The ones that had both had less impact on following traffic when the brakes were applied. If you have a clear lens model I have a writeup that shows the differences but it sounds like you have the red lens model.

 

[rocketmanli]

The one I have is a clear lens model, but has a red lens that covers it. It definitely flashes, but for a minute amount of time. I bought it on Ebay, and it did not work, so the seller refunded my money. I called Code3 who manufactures the light, and they sent me a brand new one for free-stand up guys, for sure.

Here's the old module:


Here's the new module that replaced the old p/n:


Here's how it looked when I got the old one:

 

[rocketmanli]

Here's the wiring from the old one which is identical to the new one. I cut the OEM AMP connector off the old one:

 

[Paladinwest]

I believe that one is the previous model to the ones that I purchased. The ones that I have had fewer LED's and no flashing circuitry built in. I had to add an external circuit to make it flash on the GSA's. My flasher circuit would not work on the RT because of the pulse width modulated tail light on that model. I had another circuit designed to allow for the PWM tail light but my friend with the RT was happy without the flash (he got one of the ones with both brake and tail light). Doing the install on four bikes was pretty labour intensive and to add to it one of the LED modules was defective from the manufacturer. The BMW dealer where I purchased the units (Cycle Specialties in Modesto, CA) was great to work with and replaced the bad unit immediately. I don't know why there were different units with the same part number but it made the installation very challenging. Even though it has a BMW part number it certainly wasn't a guaranteed plug and play item.

 

[rocketmanli]

This morning I tried the following. Disconnected the switched hot lead and ground from the FZ1 FuzeBlock, and connected those wires to the rear 12v accessory port via a BMW plug, and got the same results as before. Put rags over the HyperLights and OEM brake light to focus on the supplemental brake light.
Here's a couple of before and after shots to give you a better idea of what I'm talking about:

Tail Light Only:


Brake Light:


Essentially the same brightness......

 

[Paladinwest]

I think that the problem may be that these lights were intended for tail lights that had a distinct taillight and brake light feed, not the pulsed taillight/12 volt brake light of the 2009 RT. I think that the later model of light was built to deal with that issue. It is possible to build a circuit to filter out the pulsed taillight signal and only keep the brake light signal but it is somewhat complex if you haven't worked with electronics and don't have access to circuit board fabrication tools. Essentially it involves resetting a timer each time the pulsed taillight signal goes low so that when the brake is applied (constant 12 volts to the bulb instead of pulsed) the timer is no longer reset and the output turns on the LED. You end up with no tail light on the aux light, just the brake light.

 

[rocketmanli]

I'm going to run that by the Code3 techs when I hear back from them. They told me the replacement module they sent me was the latest model and that the part number T16355 that I originally had, has been changed to T07944 and is currently available. One way or another this will work out. And even if I have to keep it as it is, more lights are always better than less lights. I'd rather keep this than have the two miniature reed round reflectors I used to have there.

Their installation instructions say:
BROWN – GROUND
RED – TAIL LIGHT (+12 Vdc)
GRAY – BRAKE LIGHT (+12 Vdc)

It appears as though they are looking for a 2-wire system, although the red is still a constant hot for the running light.

 

[rocketmanli]

A $3.00 possible solution is on its way.
I give you the mini 12volt LED PWM dimmer:

It does a lot more than just dim the LEDs in 8 steps, it has 256 levels of PWM controls, but that's all I plan to use it for. Fingers crossed.....

 

[rocketmanli]

As crazy as I know this is going to sound, I found the problem just now. Can't explain it, but the LED light is now functioning perfectly. Lower brightness as a running light, and noticeably higher brightness as a brake light. All I did was unplug the red constant (+) wire from the Fuzeblock, to see what would happen. It works great. Apparently just the gray brake trigger wire is enough to make it work. Would love to know why, but sometimes it just doesn't matter.

 

[rocketmanli]

Code Tech Support just said:
"Larry,

I am pleased to know that you are satisfied. I did some checking into your vehicle and the led module based on your last email.
Your vehicle apparently uses CANBus. The original part is a CANBus Stop-Turn-Tail Module. The part that you recently received
Is a non-CANBus Stop-Turn-Tail Module. Unfortunately, Code 3 stopped providing the CANBus version of the module five years ago.
Both versions are similar.

Do you think that the red wire was always energized? The red wire is supposed to received a switched 12 volt DC signal."

 

[Paladinwest]

As crazy as I know this is going to sound, I found the problem just now. Can't explain it, but the LED light is now functioning perfectly. Lower brightness as a running light, and noticeably higher brightness as a brake light. All I did was unplug the red constant (+) wire from the Fuzeblock, to see what would happen. It works great. Apparently just the gray brake trigger wire is enough to make it work. Would love to know why, but sometimes it just doesn't matter.

Easy, you no longer have the " 12 volt taillight" enabled all the time. When the "pulsed brake light" (the normal tail light function) is on it is dimmer and when the "12 volt brake light" is on it is brighter. There is no separate brake and tail light circuit on certain incandescent tail light BMW's, like the 2009 RT (and on some that do have the two circuits if the tail light burns out the ZFE will pulse the brake circuit to provide a tail light until the bulb is replaced). The bikes that came with LED taillights (like the 2008 and onwards GS/GSA) went back to the separate brake and taillight circuits.
As far as Canbus compatibility goes, other than a handy name, Canbus has little to do with the whole process. The ZFE (body control module) looks at current draws from the "bulbs" to see that it is within a certain range. If it is too low it determines there is an open circuit (likely burnt out bulb) and sends a message over Canbus which turns on the lamp failure warning on the dash. If it sees an overcurrent then it shuts down the circuit and sends a fault message. In the case of replacing incandescents with LED's "Canbus compatible" LED's are set up to draw similar currents to the bulb that they are replacing otherwise the ZFE would see an undercurrent (since LED's typically draw less current than incandescents). Similarly, if you put too many devices on the circuit the ZFE will see an overcurrent and shut the circuit down. The software loaded in the ZFE determines the current limits and how the ZFE reacts.

 

[rocketmanli]

Excellent explanation and clears up a lot. With guys like you, who really needs to call a dealer?
I am relieved that all is now right in my world. A little trial, a little error, and dumb luck helps a bit. I learned a lot in this exercise. Thanks..

 

[Paladinwest]

Glad that I could help, even if it was by way of explanation. I spent a lot of time figuring out how the system worked so that I could make the lights that I got for myself and friends work as I thought that they should. Then I sold the bike. My friends are happy with their lights though.