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Thread: K100LT Reconnecting battery blows the horn

  1. #1
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    K100LT Reconnecting battery blows the horn

    My battery connectors on my K100lt and not color coated; all black. When I try to connect, the horn blows and I can hear the the connector trying to arc. This happened when I tried to connect what I thought was the correct way (no horn blown, but arcing sound) and when I tried another way.

    May have I have a photo of someone's K bike connected to the battery?

    I'm trying to look for an electrical issue I have had that I've posted on here about a month ago.

    http://forums.bmwmoa.org/showthread....trical-problem
    Mauser mit Dem Mauser.

    1976 R60/6
    1988 K100LT
    1975 850 Norton Commando

  2. #2
    Registered User kioolt's Avatar
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    The cable that runs down to the transmission case is the negative. As for the horn blowing when you hook up the battery. I'm assuming you mean just a short toot. Mine has done that since it was new. It's got to do with the factory alarm system. Don't worry about it. If you still have the factory alarm you should check the battery in it. The alarm system is that rectangular black box in the tool tray with the plunger switch on it. There is a 9 volt battery in it.
    2004 R1150RT 155,600 miles , 1991 K100LT 128,400 miles, 1982 R100RT 106,900 miles
    Total 390,900 BMW miles
    AMA,BMWRA,BMWMOA
    The cheapest thing on a BMW is the nut that connects the handlebars to the seat.

  3. #3
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    Quote Originally Posted by kioolt View Post
    The cable that runs down to the transmission case is the negative. As for the horn blowing when you hook up the battery. I'm assuming you mean just a short toot. Mine has done that since it was new. It's got to do with the factory alarm system. Don't worry about it. If you still have the factory alarm you should check the battery in it. The alarm system is that rectangular black box in the tool tray with the plunger switch on it. There is a 9 volt battery in it.
    I'm afraid it is not a short blow. The horn stays continuously on. I've sprayed the inside of the control switch with contact cleaner, but it has not stopped the horn from blowing, and the battery indicator light is showing with the key off (horn blows with the key off).

    Folks, I really need some help on this.
    Mauser mit Dem Mauser.

    1976 R60/6
    1988 K100LT
    1975 850 Norton Commando

  4. #4
    #13338 PGlaves's Avatar
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    It sounds to me (no pun intended) that the horn relay is stuck. It is located in the electric's box below the rear of the fuel tank. Remove the tank and box lid. Disconnect the horn. Connect the battery. Identify the horn relay by removing a relay - then touching the horn wire to the horn. When it doesn't sound you just pulled the right relay. Replace it.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  5. #5
    Registered User kioolt's Avatar
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    By reading your original post I get the impression that you have hooked the battery cables up both possible ways (reversed and correct). When you hooked them up reversed you may have blown the diodes in your alternator. It only takes a split second. Try unhooking and taping up both wires from the alternator and see if that makes your charging light go out.
    2004 R1150RT 155,600 miles , 1991 K100LT 128,400 miles, 1982 R100RT 106,900 miles
    Total 390,900 BMW miles
    AMA,BMWRA,BMWMOA
    The cheapest thing on a BMW is the nut that connects the handlebars to the seat.

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