Tail/Brake Light Failure

Discussion in 'Sportster Models' started by TheJudge, May 19, 2011.

  1. TheJudge

    TheJudge Member

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    My 1991 Sportster is giving me a challenge. First, my brake light did not work at all. I replaced the bulb and then the rear brake light switch. That fixed the problem (however, I did notice my front brake light switch also does not light the brake light).

    All was well for a while, then I noticed my rear light failed. I still had brake lights with the rear brake. This time, I found the bulb had failed. I replaced the bulb and all was well again.

    Now I noticed I have no brake light again with either the front or rear brake application. I still have rear running lights, just no brake light. I did not check the bulb yet.

    Any help??
     
  2. glider

    glider Veteran Member

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    Sounds more like a problem with the socket rather than the bulb. Check the contacts in the socket for corrosion and that they have a bit of spring action to contact the bulb.
     
  3. ckhismine

    ckhismine Active Member

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    Did you use a cheap bulb from Walmart ? Best not to be cheap on lights for your safety. The bulb is a twin filament so it possible you just got a bad bulb. Good luck.
     
  4. TheJudge

    TheJudge Member

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    I was just able to check the bulb. Both filaments are intact. I do have to keep the bike outside (no garage). It's always covered, but we have had a very wet month. Could moisture be a problem?

    I do have a service manual for the bike. I tried to follow the wiring diagram. It looks quite simple on paper. Would a short cause the problem? I came to the conclusion that a short would cause failure in both running and brake light functions since there are only two wires going into the bulb. Since I have one or the other (depending on the time line), I'm thinking not. But this is not my strong suit.

    I'm desperately trying to avoid an expensive diagnostic bill for a simple fix.

    Another thought --- Since my front brake light switch is not working right either, could it affect the operation of brake light from from the rear switch?

    Do I have to completely disassemble the throttle grip in order to access the front brake light switch in the right switch housing? That is the only thing preventing me from replacing the front switch myself.
     
    Last edited by a moderator: May 22, 2011
  5. glider

    glider Veteran Member

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    Two independent systems activating the same light. You have to open the switch housing to access the switch.
     
  6. wilks3

    wilks3 Junior Member

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    Is there a wiring connection under seat before wires go to/under rear fender? If so un-plug connection and check for voltage when either switch is applied. If voltage its not the switches. You should be able to remove wire harness from where you un-plugged it to the rear light somewhat easily and go over it for cuts. Check with meter for conductivity from harness end to light bulb socket. Takes alittle time but not hard to do.
    wilks3
     
  7. TheJudge

    TheJudge Member

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    Thanks for all your help! I actually see a firey ball in the sky this afternoon. Perhaps I can get something done.
     
  8. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

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    As the wiring to the brake light runs on the underside of the rear fender then go through the fender to the tail light unit there may a a problem with that wires
    Yes there are only 2 wires 1 for the tail light and 1 for the brake light earth return is through the frame of the bike as the 2 circuits use the same earth it should be OK
    it can be a wee bit of a pest getting the tail light off the bike as the screw heads are on the underside of the fender and could have been there for 20 years
    Fiery ball in the sky is a good sign

    Brian
     
  9. TheJudge

    TheJudge Member

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    I solved half the problem!!! Thanks to all of you! :small3d028: Turns out the rear brake switch, which I recently replaced, twisted loose. My bad for not tightening it sufficiently. I still need to replace the front brake switch.

    I'm a little confused after reading the manual. :newsmile108: Do I have to disengage the throttle cables from the twist grip to access the front brake switch?
     
  10. Jack Klarich

    Jack Klarich Expert Member

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    Replacing Front Brake Light Switch - Harley Davidson Community