BMW R1200R R1150R/T F800 K1200R R1100R/T R1250R RnineT Message Board

My taillight burned out yesterday. I discovered this when the yellow warning lamp came on and the word "LAMP" appeared in the LCD.

But the weird thing was when I stopped and checked my lights, everything seemed to be working. So, thinking "!@#$%^& computer screwed up," I rode home.

Here's what I found: The tail/brake light is a standard dual-filament 1157-type bulb. When the taillight filament burns out, the computer detects this and uses the brake light filament for BOTH functions. It applies a low voltage for the taillight function and normal full voltage for the brake light. So everything APPEARS normal.

This is explained in the manual, but not something you're likely to remember when it happens on the road. It's also worth noting if you're thinking of adding a Back-Off module or HyperLites or ElectroPods--they probably won't work right.

Hey -- I remembered reading that, because I study my owners manual ( except for the tire pressure)

Damm computers they'll make us all crazy

NeilS wrote:My taillight burned out yesterday. I discovered this when the yellow warning lamp came on and the word "LAMP" appeared in the LCD.

But the weird thing was when I stopped and checked my lights, everything seemed to be working. So, thinking "!@#$%^& computer screwed up," I rode home.

Here's what I found: The tail/brake light is a standard dual-filament 1157-type bulb. When the taillight filament burns out, the computer detects this and uses the brake light filament for BOTH functions. It applies a low voltage for the taillight function and normal full voltage for the brake light. So everything APPEARS normal.

This is explained in the manual, but not something you're likely to remember when it happens on the road. It's also worth noting if you're thinking of adding a Back-Off module or HyperLites or ElectroPods--they probably won't work right.

Actually - the Lite-Blazer from Run-N-Lites, and Run-N-Lites LED turnsignal conversion (which has a row of RED LED's down the center of the turnsignal) work just fine with the taillights.

http://www.run-n-lites.com/products.asp

Both are such low draw that even if the bulb burned out - the FZE won't see it as a "load" and will turn on the LAMP warning. Since the bulbs operate normally (one filament for running light and one for braking) with a good bulb - the functions of the two Run-N-Lites devices work just fine.

Got them on my Roadster - pics on my website actually..

http://www.eilenberger.net/R1200R_Roads ... Rindex.htm

Can't see why HyperLites would be much different. I suspect either device won't "fire" off if the running light filament craps out and the brake light filament is peforming both functions since the voltage will be too low to light the LEDs (unlike filament bulbs - LED's have a "threshold voltage" below which they won't light up).

If someone has a bad bulb - and wants to send it to me, I can try it as an experiment..

The issue isn't when things are working normally. You're right that the load of any of those LED brake light modules is negligible.

The problem might occur when the taillight burns out and the computer switches it over to "emergency" mode. Then, the reduced voltage applied to the brake light filament when it's simulating the taillight might still be high enough to trigger the LEDs. Without trying it, you have no way of knowing how the flasher circuits in those things might react.

I didn't measure the voltage applied to the bulb in the "tail" function, but I know that ElectroPods produce useful light at 3 volts, and that could be around where BMW runs the circuit.

I'm sure it won't damage anything, but you might end up with some strange light patterns. OTOH, it might give you a clue as to what's happened

Neil,

True. If you have the burned out bulb.. I can give it the acid test of reality...

Sorry, I threw out the dead bulb. But if you want to play, it's even easier. Just pull the wire for the taillight filament off the bulb connector. It's the straight one that doesn't have a solid brown wire going to it (that one is ground) and just pulls straight back (that is, toward the front of the bike).