1. After 20+ years it's time to pass the torch. If you are interested in acquiring this forum please contact support@cv-performance.com for details. Any spam will be reported and blocked.
  2. Welcome to Bike Talk, a forum for all bikers and motorcycle enthusiasts. If you are new to Bike Talk, be sure to register for free and join the conversation.

    There's always someone around willing to help out with questions or give a friendly wave back. All Harley and metric riders are welcome.

Wiring nightmare

Discussion in 'Motorcycle Tech Talk' started by stroker, Jun 8, 2010.

  1. stroker

    stroker New Member

    Joined:
    Nov 30, 2008
    Messages:
    5
    Likes Received:
    0
    Location:
    Safety Harbor, FL.
    This may be so simple that I will feel very dumb, but with the temp at 94 degees and very high humidity, Im ready to start throwing things at my bike ! Im trying to wire an aftermarket tail light on my chopped fender and can only get either the tail light on and no brake light or brake light on and no tail light. The new light has only two wires and the original HD light has three wires. Im sure Im overlooking something but cant figure it out.. Its a Sparto chopper taillight and its going on a 99 Sportster.. Need help..Thanks, Bobby
  2. FLHTbiker

    FLHTbiker Moderator Staff Member

    Joined:
    Nov 3, 2004
    Messages:
    18,516
    Likes Received:
    252
    Location:
    Oregon
    Sounds like you have a tail light only without the capacity for brake. You need a tail/brake light combo for the bike.
  3. stroker

    stroker New Member

    Joined:
    Nov 30, 2008
    Messages:
    5
    Likes Received:
    0
    Location:
    Safety Harbor, FL.
    Thanks for reading my post and replying, but this light has a double filament bulb and is advertised as a stop and taillight and is DOT approved with a window on the bottom for lighting my plate.. That is the confusing part. Bob
  4. FLHTbiker

    FLHTbiker Moderator Staff Member

    Joined:
    Nov 3, 2004
    Messages:
    18,516
    Likes Received:
    252
    Location:
    Oregon
    The key is your original was set up with three wires. Brake-tail-ground. I have heard of controllers that will convert 2 wire for brake/tail but have never used one. Was that new light designated for use on your bike or was it general purpose.
    Another point is that the new light which has two wires which one may be for tail only and the other for brake. Use your test light on the existing wires and test for which one is brake and tail. Is there a place to connect a ground wire inside the light. Also did the light come with any wiring diagrams or code.
    Stop for awhile, go drink a beer think about it and then go back to it.
  5. Wideglide85

    Wideglide85 Active Member

    Joined:
    Feb 17, 2008
    Messages:
    217
    Likes Received:
    0
    Location:
    Hastings, Nebraska
    I agree with FLHT, the new light is probably grounded internally so one wire is tail, the other one is brake.
  6. chucktx

    chucktx Moderator Staff Member

    Joined:
    Jul 5, 2005
    Messages:
    12,545
    Likes Received:
    10
    yup, what they said. the fender is the ground......it will ground from the mounting screw/bolt. the other two wires will be the run and brake light. the fender will need to be grounded well. the stock 3 wires....use a voltmeter. put the neg. probe on one wire...pos on another.....if you get a reading with the + showing on the voltmeter....digital....the black probe is on the ground wire. if you get the - sign, the pos. is on the ground wire. hope this helps a bit.......when you find the ground wire, attach it to the mount screw/stud.........
  7. Lucifer

    Lucifer Well-Known Member

    Joined:
    Mar 20, 2008
    Messages:
    3,861
    Likes Received:
    102
    Location:
    Cape Breton NS,Canada
    Your stock harness should be, red=brake,blue=running light and black is ground...solder a terminal on the ground wire and attach it to the fender mount for the sparto, like chuck said. You want to make sure you have a good solid ground connection. Bad grounds can be a real PIA.
  8. elektronikbadger

    elektronikbadger New Member

    Joined:
    Jun 11, 2010
    Messages:
    4
    Likes Received:
    0
    Location:
    Virginia Beach, VA
    I'd run the ground wire straight to the mounting screw on the light itself. After troubleshooting a "floating ground" problem on my last bike, you're better off to get the ground the whole way to the light instead of going through the fender for it. JMO...
  9. hotroadking

    hotroadking Super Moderator Staff Member

    Joined:
    Jun 16, 2004
    Messages:
    13,682
    Likes Received:
    584
    Location:
    Mouseville USA
    when in doubt always check the ground...
  10. FLHTbiker

    FLHTbiker Moderator Staff Member

    Joined:
    Nov 3, 2004
    Messages:
    18,516
    Likes Received:
    252
    Location:
    Oregon
    Wonder if he got it working? :rolleyes:
  11. more power

    more power New Member

    Joined:
    Apr 30, 2010
    Messages:
    127
    Likes Received:
    0
    That's some great advice that's been told to me more than once.:gah: Hate it when that happens.
  12. stroker

    stroker New Member

    Joined:
    Nov 30, 2008
    Messages:
    5
    Likes Received:
    0
    Location:
    Safety Harbor, FL.
    It seems everyone says pretty much the same thing so I hope to get back out to the garage tomorrow (Monday) and going to try again. I want to thank everyone who reponded to me about this frustating 5 minute job that has taken 5 days... thank you all , Bob

Share This Page