Tail light gremlin

Electrical & Ignition

  1. Smokinnjokin

    Smokinnjokin Well-Known Member

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    Ok, here's an odd one I can't figure out.
    When the lights are turned off (via dash switch) brake lights work correctly. Both come on when pedal is pressed. When I turn the lights on, both rear lamps work properly. Then, when brake pedal is pressed both left lights go out and only the right one shines.

    1) both are new 1157 bulbs, sockets are clean and greased with dielectric.
    2) wires (at least out side of the insulation) are clean and not touching anywhere.

    This seems to indicate the 2 wires for rear lights are grounding against each other somehow, right? I am wiring illiterate. I have the factory wiring diagram, but I can't seem to locate where this short is happening. Any ideas?
     
  2. 493 Mike

    493 Mike FBBO Gold Member FBBO Gold Member

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    Swap the bulbs side for side and see if your problem switches sides. Some times new bulbs are bad.
    Mike
     
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    • Ron H

      Ron H FBBO Gold Member FBBO Gold Member

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      This may not be your problem, but lemme share what I did to finally resolve my tail/brake lights that were intermittently going on and off: I ran a new-separate ground wire from one tail light housing to the body to a trim bolt. At first I connected a jumper wire to see if this worked. As guys have posted, grounds or lack thereof, can create many hassles so in any case assure good grounding on the gremlin hunt.
       
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      • dadsbee

        dadsbee FBBO Gold Member FBBO Gold Member

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        One housing is getting it's ground through a bulb filament. As noted above make sure your housing is grounded fully.
         
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        • chtampa

          chtampa FBBO Gold Member FBBO Gold Member

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          Same problems and was caused by an incorrect turn signal switch. I found a used original and unplugged the one in the column and plugged it in to test. Worked! Swapped in the used one and everything is good.
           
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          • Smokinnjokin

            Smokinnjokin Well-Known Member

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            Should I make a jumper from the back of bulb to bare metal somewhere on the body?
             
          • dadsbee

            dadsbee FBBO Gold Member FBBO Gold Member

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            Take a wire and put it under a housing retainer bolt and touch it to the other housing and see if it "lights" up. A meter is all you really need, from frame to housing, and see if you have 0.00 ohms or an open circuit. If open tighten a housing nut until you see it close the circuit and get ground.

            If both housings are fully grounded... see chtampas post above about signal light switch!
             
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