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Thread: Trailer Lights,

  1. #1
    Member Rock_skipper's Avatar
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    Default Trailer Lights,

    Sorry if there is another thread on this, but need some answers.

    I have three trailers and none of the lights work right. They work, just not right. Flip a turn signal, get the flashers, hit the brakes with the lights on and they go out, and so on.

    I have bought new harness's ( for two differant trucks) that plug into the back of the truck for the four way straight plug, but am getting mixed results.

    Is it the ground, wrong harness,,,,,?

  2. #2

    Default

    Dupont Spinner is the master at this, he fixed mine! PM him if doesn't respond.

  3. #3

    Default I'd venture a guess

    That 9 out of 10 trailer light problems are the result of bad grounding. Most trailer bond their ground (white wire) on the toungue stem and let the lights pick up the ground by bonding the negative wire to the metal frame. So many individual connections to go bad. You should go thru and clean each one.
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  4. #4
    Member Rock_skipper's Avatar
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    Default

    Thanks guys, Looks like I need to look at the trailer rather than the truck.

  5. #5

    Default

    My trouble shooting 101

    Step 1

    Using a jumper cable ground the frame of the vehicle to the frame of the trailer and see if your problems go away, make sure your grounds are good connections.

    If it makes no difference, remove jumper cable and unplug trailer.

    4-Way Flat Vehicle Connector
    Step 2

    Using a test light at the vehicle (test your test light on the battery) (a volt meter can be used instead of a test light)
    1) Clip test light ground to bare (or odd) pin
    2) With lights on place probe in brown wire socket, test light should light.
    3) With left turn signal on place probe in yellow wire socket, test light should flash.
    4) With right turn signal on place probe in green wire socket, test light should flash.
    If the above happens vehicle is ok.
    If not post what happens.

    4-Way Flat Trailer Connector
    Step 3

    Note: Do not connect trailer plug to vehicle plug
    At the trailer you will need
    1) Voltage source, jumper cables from the truck battery will work fine.
    2) 2 jumper wires.

    Connect voltage source ground wire to trailer plug (odd) socket using jumper.
    1) Connect voltage source positive wire to trailer plug brown wire pin using jumper, running lights should light
    2) Connect voltage source positive wire to trailer plug yellow wire pin using jumper, left turn/brake light should light
    3) Connect voltage source positive wire to trailer plug green wire pin using jumper, right turn/brake light should light
    Post the results of each test.

  6. #6

    Default Test Light

    Maybe not, can't hurt to take a 12vdc Test light and ground the clip to a GOOD Ground connection, clean if you have too.
    Put the end into one of the sockets and see what the test light does, write down the socket location.

  7. #7
    Member Dupont Spinner's Avatar
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    Default

    Quote Originally Posted by Rock_skipper View Post
    Sorry if there is another thread on this, but need some answers.

    I have three trailers and none of the lights work right. They work, just not right. Flip a turn signal, get the flashers, hit the brakes with the lights on and they go out, and so on.

    I have bought new harness's ( for two differant trucks) that plug into the back of the truck for the four way straight plug, but am getting mixed results.

    Is it the ground, wrong harness,,,,,?
    Let me know if you need an extra hand.....If you are working with a Chevy there was a couple of years with some issues and trailer lighting, plugs or something like that but all a workable fix. Could be a couple of things, but it is sounding like a crossed wire/short. Most likely more towards the trailers then trucks. Grounds are a great place to start after ensuring your vehicle is correct.

    Quote Originally Posted by Myers View Post
    Dupont Spinner is the master at this, he fixed mine! PM him if doesn't respond.
    Thanks for the credit.....

    Anyone needing help with Trailer lighting, brake systems or trailer repairs let me know....Making you safer on the road makes the road safer for me to be on the road.

  8. #8
    Member Bushpilot's Avatar
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    Default

    Wanted to bump this back to the top, because of a problem I'm having with my trailer brakes with a rig I have. Older 1988 Suburban with added 7 pin connector/4 pin connector.

    Found an extra wire at the battery, that runs to the back.

    When I plug the 7 pin connector in with that wire connected to positive, the trailer brakes stay on(all the lights work fine, including brake lights).

    When the 7 pin connector is plugged in, and I disconnect that wire, I can use the brakes on the trailer with the controller in the cab, but they don't work when depressing the brake itself(all the lights work fine, including brake lights).

    Seems like a simple fix, but I can't stand working on the electrical side of things. Any and all help would be appreciated.
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  9. #9
    Member Bullelkklr's Avatar
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    Default 2 standards

    there are 2 standards for wiring up the 7 pin adapter. Dodge (on some years) is different than ford or chevy. The center pin is sometimes used for charging in one standard, the other standard uses the center pin for power to the breaks.

    Google up 7 pin trailer wiring configuration and you should find some diagrams.

  10. #10
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    Default

    I own four different boats with four sets of lights. I made a set of clamp on that I can move from boat to boat. They never get wet, and are stored inside my truck when I'm out. I might look a little red neck, but I'm legal and they always work.

  11. #11
    Member Dupont Spinner's Avatar
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    Default

    As stated above there were a couple of different truck setups and some took them as standard when they went wiring things.

    Bushpilot
    Somewhere along the harness someone spliced into your truck power wire to use for your brakes. Also normally that wire does not go directly to the battery, as this would drain your truck battery down if the trailer that was connected was drawing power......willing to help if any place close to Chugiak.

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