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  1. #1

    Default Trailer light harness problem

    I cant seem to get my trailer light plug to work properly on my 03 Silverado HD. I checked the 2 red wires, 2 square fuses, and blue wire in the under hood fuse box and they are all connected and working fine. I pulled appart the plug underneath the truck behind the spare tire where the label is for the trailer light colors and functions and tested voltage there.

    Red Wire- 12v+ works as it should

    Black Wire- ground works as it should

    Yellow Wire- left turn works as it should

    The fat blue wire shows 12v when the running lights are turned on

    The fat blue also shows 12v when the brake pedal is applied.

    The stand alone blue wire shows no power on either side of its connector.

    Basically I have no right turn signal and the electric brakes are energized when the running lights are on.

    Any suggestions on what to do with this?

  2. #2

    Default

    Best to not go by wire colors, but by the positions of the pins on the female and male trailer plugs.

    Some smart person decided to use *different* colored wires for the trailer than the vehicle uses!

    So search on google.com for trailer wiring and you can find tons of information on this. Just be aware that the colors used on the truck do NOT necessarily pass through to the same colors on the trailer!

    And is the truck and all its wiring factory/stock? All done by GM?

    And is all the trailer wiring "factory"?

    If one is factory wiring and the other is not, check the wiring on the one which is not factory. Again go by the positions on the plugs, not wire colors.
    92 GMC Sierra 2500

  3. #3
    Jr. Apprentice spottweld's Avatar
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    Default trailer lights

    It sounds to me like you might have some bare wies and or a bad ground. I know that you say that your ground is good, but i have seen some bad ground problems that will astound even the best of wrenches. You need a multimeter to test continuity to see where your problem lies

  4. #4

    Default

    The entire truck harness is stock, the trailer is 3 years old and has been hooked to numerous other trucks with zero light/brake problems.

    I have chased this problem for the past 5 evenings and basically I'm out of time and out of patience with trying to track down the cluserfuk of what should and shouldnt be hooked up in the factory harness. Can anyone tell me what wire I need to tap into on the brake pedal for trigger wire to the trailer brakes?

  5. #5

    Default

    Quote Originally Posted by 28sstony View Post
    The entire truck harness is stock, the trailer is 3 years old and has been hooked to numerous other trucks with zero light/brake problems.

    I have chased this problem for the past 5 evenings and basically I'm out of time and out of patience with trying to track down the cluserfuk of what should and shouldnt be hooked up in the factory harness. Can anyone tell me what wire I need to tap into on the brake pedal for trigger wire to the trailer brakes?
    The white wire from the brake switch is the wire that eventually turns on the brake lights. It goes from the brake switch to the turn signal switch where it's separated into left and right. Here's a picture of the brake switch.
    Attached Thumbnails Attached Thumbnails brake.jpg  
    Jim

    2004 SILVERADO 2500HD LS
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    Other rides:

    1967 Landcruiser <350 Chevy>
    1970 Camaro
    1990 Geo Metro Convertible
    2007 FJ Cruiser

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