Hello new friends, i need some help with a trailer brake problem.

Discussion in 'Towing & Trailer Tech' started by MrJohnny, Aug 25, 2014.

  1. MrJohnny

    MrJohnny New Member

    I drive a 2014 GMC Sierra 2500HD, it came with a class V hitch and the trailer package....the trailer brake controller was already factory installed in the dash. Yesterday I purchased a very used 1999 Big Tex 70PI trailer with electric brakes.
    When I plug the trailer (with an adapter) into the trucks bumper, all my lights work (running, brake and turn signal lights). But the trailer brakes seem to be applied whenever the connection is made, as if I was stepping on the brake but I am not. When I disconnect the plug, the trailer will roll freely. Adjusting the "Gain" up or down does nothing.
    Does anyone know if this is an issue with my truck or the trailer? Is there wiring on my truck that still needs to be completed?
    Thank you everyone for reading my question, I hope someone can help me.
  2. ChevyFan

    ChevyFan The Sheriff Staff Member 5+ Years 1000 Posts

    Can you test it on another truck to see if is the truck or the trailer causing the problem? You've got an open circuit to force the brakes closed.
  3. MrJohnny

    MrJohnny New Member

    The trailer has rust and a bunch of visual possible electrical problems. I think I am going to rewire the whole trailer, its easier then tracing out old wires. Plus doing it this way will eliminate any other future troubles.
    Thanks ChevyFan for the suggestion.
  4. Dana W

    Dana W Rockstar 3 Years 500 Posts

    The wires may be reversed on the trailer.
  5. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    You say your using an adapter, I know what type of connector is on the truck, what do you have on the trailer?
  6. MrJohnny

    MrJohnny New Member

    The truck is a 7 blade and the trailer has a 6 pin. I am rewiring the entire trailer using a 7 blade harness. The breakaway system is a mess,,,battery dead with a big crack in it, switch was cracked and the pin is stuck inside. lol. All is being inspected and replaced correctly. Going to pull the wheels and test the brakes individually and replace if necessary. I was hoping for an easier solution but it is what it is. Buyer beware. I am more than sure this will correct all the problems.
    Thank you everyone for your help.
  7. MrJohnny

    MrJohnny New Member

    in case anyone is interested...all is fixed. the trailer was a mess, once completely rewired everything works as it should.
    I've read on some sites and message boards that some GM trucks come from the factory with towing wires in place but not hooked up(I can't imagine why). This wasn't my case...all was correctly hooked up from the factory.

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