Brake lights only stick while parking or headlights are on

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Justin352, Oct 15, 2021.

  1. Justin352

    Justin352 Bobtail Member

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    Jun 30, 2015
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    Hey everyone I'm hoping I can fi d out so.e answers here. I have a 2011 Freightliner Coronado with a Cummins ISX. I'm have trailer brake light issues. 8ve hooked to several trailers just to make sure the problem was in my truck. Whenever I have my parking lights or headlights on and I hit the brakes my trailer brake lights stick on. If I hit my marker interrupt switch or turn on my 4 ways the go off. The tractor brake lights don't stick 9n its only the trailer. Is this a wiring issue or a bad switch or relay somewhere? Thanks in advance for any and all help!
    Justin.
     
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  3. BoxCarKidd

    BoxCarKidd Road Train Member

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    Sounds to me like you have power back feeding across a circuit or a bad ground for a light causing a back feed.
    This is causing the trailer brake light relay to stay engaged until you break the circuit.
    Try breaking down the system. Unplug pigtail from truck and re connect. Unplug truck brake lights one at a time.
    This is only a guess as I am not much on Coronados but where I would start.
     
    Rideandrepair and Justin352 Thank this.
  4. Justin352

    Justin352 Bobtail Member

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    Jun 30, 2015
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    I appreciate it I will try that.
     
  5. BoxCarKidd

    BoxCarKidd Road Train Member

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    The Columbias also had connectors behind the kick panels and behind the doors that could do stuff like that. Usually kind of green looking build up.
     
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