Brake light indicator

[2whelman]

I am sure this question has been answered a thousand times, but I could not find it in the search; I added a double row LED light bar to the rear of my 85 K100 Rt and the bad bulb indicator is on now. I have read somewhere that some resistor needs to be added to prevent this. What is the procedure to buy pass or parts needed to keep the brake light check working properly with these LED lights? Thanks in advance.

[deilenberger]

I am sure this question has been answered a thousand times, but I could not find it in the search; I added a double row LED light bar to the rear of my 85 K100 Rt and the bad bulb indicator is on now. I have read somewhere that some resistor needs to be added to prevent this. What is the procedure to buy pass or parts needed to keep the brake light check working properly with these LED lights? Thanks in advance.

Actually - AFAIK - this is the FIRST time :)

The bulb monitor couldn't care less if you add an LED light in parallel with your existing brake light. BTDT on my '85 K100RT (used a Genuine JC Whitney 3rd brake light - 16 LED's in a row on top of my rear case..)

The bulb monitor is indicating you have some other problem.

The monitor doesn't just check the brake light bulb, what it checks is:

1. Brake light bulb
2. Running light bulb - ie the other bulb in the housing
2. Front and rear brake light switches - and it requires (as I'm sure you know) that BOTH be used once to turn the light off.

You can check all these functions pretty easily. IF all of these are OK, what I'd suggest doing is:

1. Replace your rear bulbs - keep the old ones as spares. Use silver based bulbs (available at most big auto-parts stores as foreign car bulbs - made by Osram/Sylvania). The bulb monitor can trigger if the resistance is high on the brake or running light circuit and a brass based bulb can cause that, as can a bulb ABOUT to fail.

If that doesn't work:

2. Disconnect and clean the large multipin connector back in the brake light housing. This housing isn't very well sealed and dirt and water can get into it. Use some electrical contact cleaner to clean the connector while it is disconnected. I do NOT recommend the use of any "dielectric" grease since the grease IS an insulator (which raises resistance.)

If that doesn't work:

3. Buy a spare brake switch. Your '85 uses the same one on the handbrake and the footbrake (and the "clutch" warning light). The one on the footbrake is known to give trouble due to moisture getting into it (they changed the design to a different switch around 1990 or so). Try unplugging each of the brake light switches and substituing the new one and pressing the plunger on it. If this cures the problem - replace the switch that cured it with your new one. If not - keep the spare in your tail-pod housing, you'll need it sooner or later.

4. If all the above doesn't work - well - now you get to the expensive bit. The manual gives the above as the troubleshooting, then says in effect "If everything else checks out OK - replace the warning light module" - which I have had fail TWICE on the K100RT. They luckily are only an arm up to about your elbow (~$40 last time I bought one) - but it does require removal of the tank to replace (it lives in the electronics box..)

HTH, and thanks for asking for the first time :clap

[2whelman]

Thanks for the response! For what it is worth, the warning light does not come on at idle, starts glowing faintly around 3500 rpm and is fully lit at 4000 + rpm. I figured a bad connection where I soldered. I have checked connections/switches/wires, BUT, I just installed new bulbs, and they are brass. Will swap them out tonight. I would not have figured that out for awhile. This forum and your input is worth its weight in gold. Wish I would have joined the BMWMOA back in 87 when I first picked up the RT.

[Hawkeye]

Hey 2Whelman:

Your post doesn't say what type of lights you added but I saw this note on Cyclegadgets website for a product called: BackOFF LED Frames.

"Brake Light Module works with BackOFF LED frames, your stock brake light, or both simultaneously. Simple 2-wire installation converts your brake lights to pulse in an attention-grabbing pattern whenever you apply your brakes. Not recommended for use with R1150RT stock brake light - it will cause your "Brake Light Out" light to remain lit. It will work fine on the R1150RT flashing a BackOFF license frame."

Good luck.

[2whelman]

The LED units are the license plate frame type, but not the modulating type.

All items are checking out ok, so must be the bulb monitor unit.

[davel]

I think his initial email is correct. I went through the trouble of converting my 91Krs tail light to a 1157 so that I could use my bulb that flashes and then goes solid when you apply the brakes. I had the same problem the brake indicator like stayed on. It has something to do with the low resistance or wattage of the leds. I settled for a higher intensity 1157 bulb, but would like to be able to use the other one. Only Options I know are to ignore the light which is hard to do at night, or remove the bulb from the cluster which defeats its purpose... :dunno

[2whelman]

I have read quite a few articles about the need for resistors for this purpose and I really thought that was the problem. I went through the trouble shooting step by step as suggested and even disconnected the LED light bars.
The bulb monitor is still coming on, so the only item left is the monitor relay. I may just pull the bulb in the instrument pod, vs replacing the relay. I usually check my tail/brake lights before each days ride anyway, plus, the LED unit acts as a redundant system. I guess I can always replace the unit next time I have my tank off.

As always, thanks everyone for the input.