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Trailer wiring question

Discussion in '2nd Gen. Tacomas (2005-2015)' started by PA452, Jun 18, 2014.

  1. Jun 18, 2014 at 8:29 PM
    #1
    PA452

    PA452 [OP] Well-Known Member

    Joined:
    Apr 28, 2007
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    646
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    Male
    Western PA
    Vehicle:
    15 Access TRD Offroad, V6, 5spd Auto, 4x4
    I have a factory towing package setup on my 2007 Tacoma. It has a round 6 or 7 flat pin plug (can't remember 6 vs 7 at the moment). I sometimes borrow a friend's trailer that uses a 4-pin plug. I bought an adapter and it works great during the day. The signals and brakes work fine. But once I turn on the truck headlights, the trailer lights will come on and no longer work with the brakes and signals. The trailer lights are on, but it's like I'm driving around with the trailer brake lights on 100% of the time as long as the truck headlights are turned on.

    Any ideas?

    Thanks
     
  2. Jun 18, 2014 at 8:56 PM
    #2
    Jimmyh

    Jimmyh Well-Known Member

    Joined:
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    Prerunner SR5
    Since your is wired factory 7 flat connector using an adapter 7 to 4 flat I would guess there is an issue with the trailer wiring or the type of lights that are installed on it. Do you have a multimeter and know how to use it? If not you could get one of these testers:

    Reese Towpower 74633 4-Way Tester
    http://www.amazon.com/Reese-Towpower-74633-4-Way-Tester/dp/B000CP8FU0


    * The ground pin is the one that is exposed on the Truck Side of the connector. The pins are left to right:

    Truck Side Connector:
    Ground |Tail | Left Turn | Right Turn
     
  3. Jun 19, 2014 at 5:10 AM
    #3
    OCNutty

    OCNutty Well-Known Member

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    Northern, Va.
    Vehicle:
    Silver Prerunner DC v6 SR5 Tow
    There's a wiring problem somewhere in the trailer lights.
    It seems like there is an additional connection between the running lights pin and the trailer lights.
    So, what i read is, as long as the headlights are off, there is no power to the running lights pin on the connector, and the trailer lights are normal (brake, and turn signals)
    As soon as the highlights come on, power to the running light pin on the trailer connector, which should be fed ONLY to the running light (low intensity filament) on the trailer, is also fed (cross connected) to the trailer lights stop/turn (hi intensity) filament(or led), overriding brake and turn signal functions with full time 12v.
    The trailer owner has a cross connection (and or other problems?) in this trailer harness.
     
  4. Jun 19, 2014 at 6:05 AM
    #4
    jethro

    jethro Master Baiter

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    Southern NH
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    13 Access 4x4 TRD Offroad
    Empty gas tank mod
    Almost all problems with trailer lights are grounds. Check the grounds on the trailer. Your truck harness is likely not the problem.
     

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