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Thread: K75S '91 Brake warning light

  1. #1
    Registered User plehman's Avatar
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    K75S '91 Brake warning light

    When I use the front brake and the back brake together the warning light goes on. The same light that has always gone away once I tap the front and rear. Does not happen one at a time.

    Leading up:
    Burnt out the brake bulb. Easily replaced from the auto parts store.
    Put in the bulb and when it didn't work I tried the fuse. Indicated on the box as Brems Schuss Licht. Cool. I assume that's Brake Stop Light auf Deutsch. Replace fuse and the brake light worked fine.

    But on the way to work this morning after the above fix and I started seeing the warning light every time I use both brakes together. Very distracting.

    The Pads are on the low side, but I don't think there is a pad wear warning light anyway.

    Any ideas?
    thanks!

  2. #2
    Rally Rat
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    Is the new brake light illuminating when both brakes are applied and the warning light is illuminated?

  3. #3
    Registered User plehman's Avatar
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    Yes, new brake light works independently with both front and back, but when both are applied simultaneously the warning light also goes on. It's like it goes into the initial system check. Note this just started and doesn't happen with just front or just rear.

    How does that initial warning circuit work?

  4. #4
    Registered User plehman's Avatar
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    Another thought. Could it be the warning light relay? (no ABS by the way).

  5. #5
    RS MotoBrick owrstrich's Avatar
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    the first thing I would do is make sure the new brake bulb is the right wattage...

    link to snowbums piece...

    http://bmwmotorcycletech.info/K-hints.htm

    j o

  6. #6
    Registered User plehman's Avatar
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    Resolved

    Wow, the Brake Monitoring Unit (BMU) really didn't like a bulb from Napa. Well the bulb worked but it triggered a fault in the system. I just went to Greater Boston Motorsport and bought a 10W brake light bulb ($1.27) and it now functions normally. I think that's fussy but glad it's resolved.

    thanks very much for the tip.

  7. #7
    3 Red Bricks
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    What was the wattage of the bulb from NAPA?



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  8. #8
    Registered User plehman's Avatar
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    The replacement bulb from NAPA was only 5w, so I thought it was safe.

  9. #9
    3 Red Bricks
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    Why would you put a 5w bulb or even a 10w bulb in the brake light when it calls for a 21w bulb???

    The taillight calls for a 10w bulb.

    No wonder it didn't work properly. The bulb monitor is resistance sensitive.

    There are many cars that the same thing is true for. There are some that will render the cruise control inoperative if the incorrect bulb is used, even if it is the same wattage.




    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  10. #10
    Registered User plehman's Avatar
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    [QUOTE=98lee;900928]Why would you put a 5w bulb or even a 10w bulb in the brake light when it calls for a 21w bulb???

    The taillight calls for a 10w bulb.

    No wonder it didn't work properly. The bulb monitor is resistance sensitive.

    Why would I put in a 5w when I know it calls for 10? Why would I go on forum if I knew everything? Not one but two shops, one a BMW shop thought you could put different watt bulbs in. Now I know it's resistance sensitive - that was my question. Not all bikes are. I thought the spirit of this forum was to learn.

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