Problems with LED headlight install. Help, please.

Home Forums All Things 750 Twin Technical Garage Problems with LED headlight install. Help, please.

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    Hi everybody,

    I tried installing the headlight in the picture on my ’79 twin.  It is an LED projector style headlight with high/low beams, LED running lights, and LED turn signals (the running lights and turn signals are the white “half moons” on the right and left of the light that you see in the picture).

    The problem I’m having is with the running lights and turn signals.

    The way the lights connect is there is a common ground for ALL lights that is connected to the ground pin on the 3 prong plug that plugs in to the hi beam/low beam plug.

    The running lights need a constant 12V.  The turn signals are wired separately, so you plug one wire into the left t/s wire on the harness, and the other on the right t/s wire.

    When the bike power is on, the running lights (both of the half moons) will always be on (color is white), whether you have the headlight on or off.

    When you click on the turn signal, the running lights turn off, and the half moon for the direction you are turning turns orange, and then starts flashing.

    My problem is that, when I click on the turn signal, the running lights do turn off, the turn signal light does turn orange, and it flashes, but rather than turn on and off when flashing, it stays lit the whole time, gets a little bit brighter with the first flash, then a little bit dimmer with the second flash.  So, rather and on/off/on/off, it is bright/dim/bright/dim.  This makes it extremely difficult for anyone to actually see that you have the turn signal on .

    I already have an LED flasher unit on the bike, because my current headlight has LED turn signals, but with a halogen H4 headlight bulb.  Those work perfectly.

    I just don’t know why they won’t turn on and off.

    ALSO, regarding the running lights, I took the 12V constant power from a spare brown wire with white stripe that is in the headlight bucket.  IF I disconnect the power to the running lights and only keep power to the turn signal wires, it blows the fuse for the tail light circuit.  Also, unfortunately, it also blew out the brake light failure switch that the bike has.  So, the running lights MUST be hooked up to power, or TAIL fuse and brake light failure switch blows.

    I’m a bit baffled, folks.  Any information would be helpful.  Thank you.!



    I am no expert on wiring LED lights but I do believe they are terminal sensitive and only work when current passes through one way. From what you are describing it sounds like when the indicators are switched on the live is constantly connected and rather than being switched on and off by the relay and is just being weakened. That leads me to think the problem is in the indicator part of the circuit and taking into account what my understanding above that points me towards the relay operation. Again not fully understanding LED components my first thought would be to try reversing the connections on the relay.



    Hi KK,


    I have to agree with your assessment.

    Unfortunately,  if I remember correctly,  I did try reversing the leads on the relay and had no change.  Being that I’m getting older and forgetful,  I’ll try again, just in case I forgot lol!


    Thanks for your response.  I appreciate it.

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