Tail lights and front marker lights won't turn off

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Josiah Harder, Dec 24, 2022.

  1. Josiah Harder

    Josiah Harder Light Load Member

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    Ignition is off and all switches are off but still can't get these lights to turn off. It's odd because after I realized they wouldn't turn off I left the yard for 5 minutes and came back to them off but then several hours later they were on again.

    I found the fuse that will turn them off its labeled 1 in my picture. Though last night in the dark I could see even with that fuse out the tail lights had some residual power and were on but very dim. So I took fuse number 2 out and the left taillight went out completely and fuse 3 took out the right taillight completely.

    I've taken the relay labeled marker clearance lights out and that also will turn them off but replacing the relay with a new one doesn't fix the problem

    Even the licence plate light is stuck on IMG_20221223_085953~2.jpg IMG_20221223_091225.jpg IMG_20221223_085904_edit_130565770507160.jpg . Really don't wanna bring the truck to the shop for something silly like this haha
     
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  3. Banker

    Banker Road Train Member

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    I had a similar issue that may or may not be the same as yours but it’s worth a look. My marker lights would come on occasionally without the switch being turned on. It was a ground wire with a worn spot in the insulation behind the switch panel grounding out and completing the circuit allowing the lights to come on.
     
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  4. Josiah Harder

    Josiah Harder Light Load Member

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    Thanks for that suggestion I'm going to take a look into that
     
  5. Banker

    Banker Road Train Member

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    It was extremely small spot and difficult for me to see. While I was in there I padded several other potential problems with wire loom. My heater blower controller did this also.
     
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  6. 062

    062 Road Train Member

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    As many computers/modules that they put in these new trucks. I would try unhooking the batteries for 15min or longer.
    @pushbroom @Goodysnap
     
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