NEED HELP: Possible electrical problem Yamaha DT50

Discussion in 'Thumpers' started by Tengai In Toronto, Dec 16, 2011.

  1. Tengai In Toronto

    Tengai In Toronto Been here awhile

    Joined:
    Apr 26, 2011
    Oddometer:
    186
    Location:
    Toronto
    Ok so my new to me '94 DT50 has been acting a fool:

    Rear brake light switch internals have melted, seizing the switch in the ON position. This means that the brake light is now always on. When the key is in the on position, the spring connecting the switch to the brake pedal heats up and sheds some sparks.

    Just wondering if the electrified brake pedal/spring is a result of the melted switch, or if the melted switch is the result of some kind of grounding problem or something? If the problem is as simple as the switch, what would have caused it to melt in the first place??

    I cleaned the melted plastic out of the switch and tried to reuse it but it gets stuck in the ON position and smoke starts coming from it within 15 seconds.

    Somebody throw me a bone because clearly i'm electrically challenged.

    Thanks,

    -The Artist Formerly Known As Tengai In Toronto
    #1
  2. Tengai In Toronto

    Tengai In Toronto Been here awhile

    Joined:
    Apr 26, 2011
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    186
    Location:
    Toronto
    Guys, come on.... Theres no way that the 33 people who have read this are less electronically/mechanically inclined than me. If I install a new switch it may just get melted again! Is that something you want on your conscience?? IS IT??
    #2
  3. Beezer

    Beezer Long timer

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    Anchorage, formerly Spenard (hub of the universe)
    that spring connects to a set of contacts inside the switch. The spring pulls the contact into place to make the electrical connection for the light. BUT, the spring is supposed to be insulated from the electrical contact and yours is not.

    should be able to fix it with a switch replacement. there may be another problem too, but the switch is bad.

    a quick check of the rest of the system would be to remove the wires from the switch and then jump the wires together, making the connection the switch would have made. the light should come on and the wires should not get hot (or blow a fuse)

    if no light and/or there is sparks & heat then there is a shorted (grounded/earthed) spot on the wire between the switch and the light, or possibly inside the light fixture itself
    #3
  4. strongbad

    strongbad Been here awhile

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    Idaho Falls, ID
    My guess is that the switch failed first, but we have no way of knowing for sure. Electrical contacts fail when the resistance across them increases which causes more heat which causes more resistance in a vicious circle until the contacts fail completely. The switch may have gotten wet which started the cycle.

    Why didn't your fuse blow? Maybe you should check your fuse to see if it's the designed value.
    #4
  5. Tengai In Toronto

    Tengai In Toronto Been here awhile

    Joined:
    Apr 26, 2011
    Oddometer:
    186
    Location:
    Toronto
    Awesome! Thanks guys, I'll look into it! The switch was definitely wet inside.
    #5
  6. 2 stroke love

    2 stroke love Dt50 1989 LC

    Joined:
    Jan 22, 2013
    Oddometer:
    2
    Hey, I have 3 of these bikes. Give me a shot, we'll figure it out.
    #6