Brake light problem - K-Bikes.com - Excellence in Motion
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post #1 of 34 (permalink) Old Jan 23rd, 2006, 2:39 am Thread Starter
 
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Brake light problem

Hello all!!

First post........

Today I fullfilled a dream. I bought a 85 K100RT from a buddy. I have discovered something that my buddy did not know..

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...

What should I do??? I have this gorgeous new bike and cant ride it because I have no brake lights!!!!

HELP!!

Thanks, Tim

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.

Thanks!

Last edited by Bowcop; Jan 23rd, 2006 at 3:03 am.
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post #2 of 34 (permalink) Old Jan 23rd, 2006, 10:28 am
 
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Hth

Quote:
Originally Posted by Bowcop
… does not appear to be a double fillament bulb
My 87 K100RS had a dual element bulb there. I do know you can get a single element bulb (an 1156) into the socket, which by design will light brightly as the single contact will receive current from BOTH contacts in the OEM socket. AFAIK, 1157 is the bulb. Bulbs HTH.
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post #3 of 34 (permalink) Old Jan 23rd, 2006, 10:44 am
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1157 is teh correct body, but .....

Quote:
Originally Posted by Bowcop
.... I bought a 85 K100RT from a buddy. .......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,....

PS, can anyone advise the bulb # that should be in there? .....
All K75, K100 ,K1100 BMW taillights are dual element. I'd second the guess that someone placed an 1156 in there. In addition to Mintaka's info...
  • Correct bulb = P21/5W
  • Will fit (as already posted), but slightly different wattage = 1157
  • Best bulb = 2357
Lots of illumination available here.

p.s. Don't use an LED unless it has side LED's. The straight on LED bulbs are crap in a "reflector" type of housig design. They look great straight on, but flat out suck from an angle. (However, I do have two NEW 1157 LED's for $5 plus shipping if anyone wants to get hit, or use them in a car.)

Last edited by CABNFVR; Jan 23rd, 2006 at 10:49 am.
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post #4 of 34 (permalink) Old Jan 23rd, 2006, 11:19 am
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Quote:
Originally Posted by Bowcop
Hello all!!
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.

Thanks!
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!

Bob.
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post #5 of 34 (permalink) Old Jan 23rd, 2006, 11:24 am
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Quote:
Originally Posted by CABNFVR
Don't use an LED unless it has side LED's. The straight on LED bulbs are crap in a "reflector" type of housig design. They look great straight on, but flat out suck from an angle. (However, I do have two NEW 1157 LED's for $5 plus shipping if anyone wants to get hit, or use them in a car.)[/i][/color]
They probably won't work anyway.

This bike has a bulb monitoring device, and unless the LED brake light has a dummy resistor to allow it to draw as much current as a normal tungsten light, the sensor will probably not sense enough current and will "think" the brake light is burned out.

Bob.
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post #6 of 34 (permalink) Old Jan 23rd, 2006, 11:27 am
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Agree .........

Quote:
Originally Posted by RFWILSON
They probably won't work anyway.

This bike has a bulb monitoring device, and unless the LED brake light has a dummy resistor to allow it to draw as much current as a normal tungsten light, the sensor will probably not sense enough current and will "think" the brake light is burned out.

Bob.
True, it's just that they aren't worth concidering in the first place. I did a side by side with the Ducati ST2 and the RS in the basement, and straight on the LED looks great. At an angle it's just awful. They make LED's with the resistor, but I'll stick to, and recommend, the 2357 bulbs.
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post #7 of 34 (permalink) Old Jan 23rd, 2006, 12:28 pm Thread Starter
 
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Some great advise here, thanks to all of you.....

I will let you know what happens.

Tim
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post #8 of 34 (permalink) Old Jan 23rd, 2006, 1:42 pm Thread Starter
 
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ARGGGG!!!!

I went and bought a 1157 and it does not fit, tried it both ways, the contact point at the bottom of the socket does not make contact with both points on the bulb.....

Any other ideas???

This is going to cost a small fortune!

Tim
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post #9 of 34 (permalink) Old Jan 23rd, 2006, 1:45 pm Thread Starter
 
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Quote:
Originally Posted by RFWILSON
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.


Bob.
My light does come on and goes out as soon as I hit the back brake.....
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post #10 of 34 (permalink) Old Jan 23rd, 2006, 2:41 pm
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Quote:
Originally Posted by CABNFVR
True, it's just that they aren't worth concidering in the first place. I did a side by side with the Ducati ST2 and the RS in the basement, and straight on the LED looks great. At an angle it's just awful. They make LED's with the resistor, but I'll stick to, and recommend, the 2357 bulbs.
I agree totally. Some people get carried away with the gimmick of having LED brakelights, but inreality there is no significant advantage. And, no, the 50 to 100 milliseconds that LEDs come on faster than an incandescent results no significant decrease in stopping distance. At 30 MPH, in 100 milliseconds you will have travelled only 4 feet; a mere half a bike-length.

Bob.
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