Originally Posted by Bowcop
It appears that the brake light is stuck in the "on" position. I checked the bulb and it is VERY bright and does not appear to be a double fillament bulb, next I checked the obvious with the switches on the front and rear brake, neither are sticking and appear to be clean...
PS, can anyone advise the bulb # that should be in there? there are two differant ones, one is the licence plate light and the other is the brake light.
Are you SURE that the rear brake switch isn't screwed? I have an '86 K100RT, and got so sick of replacing the switch located by the rear brake peadal (where it always gets soaked), that I made a completely sealed electronic switch to replace it.
If both switches ARE OK, then the problem is almost certainly in the brake monitoring unit located in the electrical box under the back end of the tank. This device turns on the red warning light on in your instrument cluster (the one with the warning triangle and "!" in the center) ever time you start the bike. It only goes out when the electronics sense that you have successfully activated both brakes, and that the light has actually turned on in both cases. It also will activate when you are riding and the light fails to goon when you apply the brakes.
If the monitoring unot is shot, you can temprarily wire around it (you should be able to figure our how by looking at the wiring diagram), and used ones show up on Ebay from time to time.
One more thing. Be sure that you check the switches IN POSITION. These switches have a little plunger sticking out, that must be pushed all the way IN to turn off the brakelight. If things are improperly adjusted, and the plunger is pushed all the way in, the light will stay on.
The rear brake switches were such a problem that BMW later used a different swich located in an area that doesn't get exposed to the elements as much.
One more thing. The bulb most certainly **IS** a double filament type! One for the tail light and one for the brake light. If it isn't, then THAT is the problem! There is only one bulb back there, so it **MUST** be a double filament type, otherwise how could you expect it to have both tail and brake light functions? Maybe some bozo just put in the wrong bulb!