1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Marker lights under tailgate

Discussion in '6.9L IH & 7.3L IDI Diesels' started by SLittle, Jun 20, 2019.

  1. SLittle

    SLittle Registered User

    Posts:
    43
    Likes Received:
    11
    Joined:
    Sep 4, 2018
    Location:
    Iowa
    1991 F350 Dually

    Under the tailgate yet above the bumper are three red marker lights. They haven't worked since I've owned the truck.

    Replaced the lights with some LED markers but there isn't any power to the lights. The rear fender marker lights do not have power either.

    Without troubleshooting the entire harness, I think it would be much easier to just splice wiring in to my trailer plug.

    So these lights under the tailgate.... were they on with the tail lights or on with the brake lights?

    (On anytime the headlights are on or only on when you press the brake?)
     
  2. Kizer

    Kizer Supporting Member Supporting Member

    Posts:
    404
    Likes Received:
    30
    Joined:
    Mar 22, 2007
    Location:
    Denton, Texas
    They are supposed to come on with your running lights.
    I don't have a diagram in front of me but I believe that's a brown wire.
     
  3. SLittle

    SLittle Registered User

    Posts:
    43
    Likes Received:
    11
    Joined:
    Sep 4, 2018
    Location:
    Iowa
    Yup. Marker / tail lights is brown wire in trailer wiring. I'll just tap that wire for all the fender and tailgate lights. Thanks.
     
  4. chillman88

    chillman88 Supporting Member Supporting Member

    Posts:
    2,512
    Likes Received:
    1,505
    Joined:
    Feb 22, 2017
    Location:
    Central NY
    Check the trailer relay under the hood by the brake booster. That powers the lights under the tailgate and the fender markers. Been there myself on my truck.
     
  5. snicklas

    snicklas 6.0 and Loving It!! Staff Member

    Age:
    45
    Posts:
    5,327
    Likes Received:
    1,225
    Joined:
    Aug 7, 2006
    Location:
    Greenfield, Indiana
    Make sure the trailer lighting relain in place. On the dually trucks, the power for those lights is supplied by the trailer relay.
     
    Jimbanjer likes this.
  6. SLittle

    SLittle Registered User

    Posts:
    43
    Likes Received:
    11
    Joined:
    Sep 4, 2018
    Location:
    Iowa
    Looks like previous owner bypassed the trailer relay???? The trailer plug is spliced in to the tail lights and the brake controller is an aftermarket add on.
     
  7. chillman88

    chillman88 Supporting Member Supporting Member

    Posts:
    2,512
    Likes Received:
    1,505
    Joined:
    Feb 22, 2017
    Location:
    Central NY
    Check the relay anyway. That could even be why they bypassed it. Mine was bad when I bought the truck, and the mounting bracket was missing. Replaced it and not being properly mounted it got water in it and stuck on. Then I got smart and replaced it with a standard Bosch style relay and screwed it to the fender.

    This is what the stock relay looks like:

    [​IMG]

    Here's my personal fix:

    [​IMG]
    [​IMG]
     

Share This Page