Swapped halogen to LED and now have a light out

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Dave1837, Apr 2, 2021.

  1. Dave1837

    Dave1837 Road Train Member

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    The trailer I pull originally had all halogen lights with the exception of one turn signal that was LED. I had a bunch of LED lights, all of the same brand, in my garage so I replaced all of the halogens with the LEDs. Now I have a rear marker light that will not work. When I put a halogen in its place, it will work until I apply the brakes. When the brake lights comes on, that light goes out. Also, when I turned the marker lights off and applied the brakes, the marker lights on the passenger side of the trailer came on. I'm thinking the whole trailer may need re-wired, I was wondering if it would be possible to run a single jumper wire from another rear marker to power the marker that won't come on?
     
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  3. AModelCat

    AModelCat Road Train Member

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    LED lights are polarity sensitive. Are they hooked up properly?
     
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  4. Racer 85

    Racer 85 Bobtail Member

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    Double check your ground wire's, I had one ground the right side fine but lost f
    Double check your ground wire's, I had one work fine on the right and apply the right and loose half the trailer
     
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  5. Racer 85

    Racer 85 Bobtail Member

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  6. uncleal13

    uncleal13 Road Train Member

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    How new of a truck do you have?
    I’m just wondering if the truck is programmed to watch for traditional lights on the trailer circuit. With the LED lights drawing way less power, maybe the truck is causing the issue.

    Don’t know, just an idea to watch out for.
     
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  7. Rideandrepair

    Rideandrepair Road Train Member

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    I would check the 7 wire receptacle where pigtail plugs in first.
     
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  8. Dave1837

    Dave1837 Road Train Member

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    It's a 2015 Mack
     
  9. Dave1837

    Dave1837 Road Train Member

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    I thought that may be the problem too, but a few weeks ago I wrote the trailer up for no ABS and they replaced that whole plug/box as part of the repair
     
  10. Dave1837

    Dave1837 Road Train Member

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    I would assume so, the plugs will only go on one way. The only ones I didn't replace were the top 3 clearance lights on the back of the trailer, which are also brake lights. Forgot to mention that in the original post. I heard somewhere that LED and halogen brake lights will cause a "train signal" when you apply the brakes? Maybe I'll try swapping those
     
  11. jamespmack

    jamespmack Road Train Member

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    Some, not all.
     
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