BMW K1200, K1300, and K1600 Forum banner

1 - 1 of 1 Posts

·
Registered
Joined
·
46 Posts
Discussion Starter #1
:wtf:
For those who installed a BRAKE ! LED unit in their Clear Alternatives tail-light assembly like I did, here is something to watch for. I had my K1200R in for replacement of a failed fuel quantity indicator tape (in the tank) on Friday. My BRAKE ! flashing led brake light and tail light worked fine until the bike was ready to ride home. Mechanics said they had to update the chassis computer (not the engine managment one) in order to calibrate my new gauge sending unit. Now the BRAKE ! brake-light would only flach on one or 2 brake applications, then illuminate the LAMPR warning message. At that point only the tail-light continued to illuminate. BRAKE ! unit got hot to the touch. One mechanic astutely suggested just wiring the old bulb connector in parallel and substituting it in for the BRAKE ! if I got this fixed somehow. Little did he know then that this IS the FIX.

I spent some hours this weekend working the problem with my BRAKE ! Led assembly. What I found was that there was no fault in the BRAKE ! unit. It worked perfectly when tested off the bike. I tried unsuccessfully to substitue other "bypass" resistors for the 75 ohm one that was already installed outside the case on this unit as supplied from the vendor. I tried a 50 ohm, 100 ohm and 10 ohm 10 watt ceramic wirewound resistors. 50 and 10 ohm worked for a short time (5 or 6 brake applications) before growing very hot and then triggering the LAMPR fail indication. 100ohm did not work at all to clear the problem. Taking out this external resistor which appears to me to jumper the tail-light power supply terminal to the brake-light power supply terminal did not help either. I then got frustrated with these resistance games and did what my mechanic suggested in the first place...just wire in parallel the original bulb and socket so you can swap out on the road in the event of failure. Voila, Eureka, and such...This works. The BRAKE ! unit functions perfectly and the original bulb provides the proper loads for this new chassis computer software load. So I just carefully located the "hot-spare" connector and bulb under the rear seat, being careful to keep it off any plastic and wiring there since the "ballast" bulb gets hot. Thinking about why this works and the original crossover resistor no longer does, leads me to believe this "new" chassis computer software is looking for independent "loads" of the tail-light and brake-light circuits. If it sees one circuit feeding voltage to the other (as would be the case if a bulb filiment failed and touched the other filiment) it indicates a fault and reverts to just a tail-light. I suppose I could fiddle around and find two ideal resistors that would provide the proper loads for each light circuit when terminated to ground, but this spare bulb using the original connector approach is easy, foolproof, and gives me a redundancy in case the BRAKE ! unit really does fail someday. If my ballast "bulb" fails, I will get a LAMPR and thus know to check and replace the bulb.
How elegant a fix. Thanks to the guys at Gateway BMW, St. Louis...

:teeth
 
1 - 1 of 1 Posts
Top