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Thread: A problem with boat trailer lights

  1. #1
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    Default A problem with boat trailer lights

    I just rewired an old trailer I bought last week.
    New LED lights with all new wiring. The lights work but are very dim and I don't know why.
    Both lights are grounded to shiny bare metal as is the ground wire at the harness end.
    I appeal to the wisdom of the Forum for any advice.
    Thanks!
    I was born on a wooden boat that I built myself.
    Skiing is the next best thing to having wings.

  2. #2
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    Default Re: A problem with boat trailer lights

    To eliminate the question about adequacy of ground, you could run a temporary jumper wire from light ground to trailer harness ground.

  3. #3
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    Default Re: A problem with boat trailer lights

    Have you checked the connector/ plug/ These get beat up.
    Have you checked the vehicle wiring? If you put a meter on your truck's plug, do you get 12 volts?

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  4. #4
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    Default Re: A problem with boat trailer lights

    Check the battery voltage directly at the battery, then at the frame ground, then at individual wires at each end with a voltmeter, you should be seeing something like 12.7 volts at every connection. The problem will soon become apparent.

  5. #5
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    Default Re: A problem with boat trailer lights

    You might test the lights by connecting directly to the battery. If they are still dim, that's your problem.

    Are you sure you wired the lights in parallel and not in series?

  6. #6
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    Default Re: A problem with boat trailer lights

    Could there be a polarity problem ? ? LED's are, after all ' light emitting diodes' ( and diodes flow current one way )





    Rick
    Charter Member - - Professional Procrastinators Association of America - - putting things off since 1965 " I'll get around to it tomorrow, .... maybe "

  7. #7
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    Default Re: A problem with boat trailer lights

    Quote Originally Posted by MarkW6 View Post
    To eliminate the question about adequacy of ground, you could run a temporary jumper wire from light ground to trailer harness ground.
    I knew the plug was good because it is new.
    I knew the battery was good because the lights on my other three trailers work fine.
    Then I tried your temporary ground wire from the lights to the harness ground in the front of the trailer.
    Success!!
    Somewhere along the length of the trailer, there is bad continuity. Probably caused by paint or rust. I've never come across that before.
    You have my sincere thanks.
    Stuff like this keeps me up at night.
    I will now make the temporary ground wire permanent.
    I was born on a wooden boat that I built myself.
    Skiing is the next best thing to having wings.

  8. #8
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    Default Re: A problem with boat trailer lights

    I've given up on using the trailer as a ground. Just too much frustration after a few years of corrosion set in. The last time I wired my trailer I used some 7 strand trailer wire and made the purple the second brown and the blue the second ground. Then just snipped off the red. No trouble so far!

  9. #9
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    Default Re: A problem with boat trailer lights

    ^^^
    When I switched to Truckite brand sealed lights 30 years ago, they have a designated ground wire (black) and I just wire them to a ground wire all along the way to the trailer plug.
    I have seen plenty of bolted together trailers that only one side was an adequate ground, and I have even seen pick-up trucks that the bed itself only had intermittent or partial ground (like when it hit a bump!)
    The best ground set-up I have ever seen is Caterpillar tractors which weld a 3/8" thick Stainless steel cleat with a threaded hole in it to the frame, using a Stainless steel bolt for the ground connection.
    I like soldered connections, and shrink tubing with internal "glue" My canoeyawl has had the same wiring on the trailer for 20+ years, once every five years or so I install a new plug end. That seems to take the worst of it corrosion wise. I never unplug my lights going in or out, it's sort of cool to see them working underwater!

  10. #10
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    Default Re: A problem with boat trailer lights

    Solder and shrink tube definitely the way to go. I chased my tail on one trailer trying to figure out the problem, turned out the ground wire had corroded well into the interior, hidden by the insulation. It looked OK on the end but there was enough resistance down the line to mess with the lights.

    The vehicle plug is easy to overlook too. My boat trailer gets two dunkings most years (one to haul the boat out for spring outfitting, the other putting the boat back in) so it doesn't take much of a beating, unlike the under the bumper plug that is being sprayed with dirty rain water 9 months out the year. Not to mention whatever it is they put down to melt snow. The one on my 22 year old Suburban is looking pretty rough, since she's a work truck now I'm considering how best to mount a new one someplace dry like in the cargo bay. I think there is enough room to run the wires flat through the rubber trim between the cargo hatch and frame.
    Steve

    If you would have a good boat, be a good guy when you build her - honest, careful, patient, strong.
    H.A. Calahan

  11. #11
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    Default Re: A problem with boat trailer lights

    I don't solder my spices, but I do use shrink tube. I've now got LEDs on all four trailers.
    Three are boat trailers that get dunked all summer long.
    The biggest decision I have every summer day when I wake up is which boat to take out on the lake.
    I was born on a wooden boat that I built myself.
    Skiing is the next best thing to having wings.

  12. #12
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    Default Re: A problem with boat trailer lights

    Are the lights grounded out to the trailer frame, or directly to a ground wire?

    Always run direct ground wires (the frame still needs to be grounded, because... shorts.)
    You would not enjoy Nietzsche, sir. He is fundamentally unsound. P.G. Wodehouse (Carry On, Jeeves)

  13. #13
    Join Date
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    Default Re: A problem with boat trailer lights

    Can you measure the voltage at the light when they are on? That measurement will tell you what is wrong.
    The other and real possibility is not the trailer at all, with todays electronics in cars a cheap Harbor Freight (or Shucks or ....) converters can cause lots of problems, my car which is a '06 absolutely requires the $100.00+ OEM adaptor and wire harness.

  14. #14
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    Default Re: A problem with boat trailer lights

    Quote Originally Posted by Nicholas Carey View Post
    Are the lights grounded out to the trailer frame, or directly to a ground wire?

    Always run direct ground wires (the frame still needs to be grounded, because... shorts.)
    That's what I ended up doing and problem solved (post#7).
    Thanks everyone for your help.
    I was born on a wooden boat that I built myself.
    Skiing is the next best thing to having wings.

  15. #15
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    Default Re: A problem with boat trailer lights

    Problems like this pop up on tilt trailers, crummy ground through the pivot point.
    Cheers
    Kent and Skipper
    Small Boat Restoration blog

  16. #16
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    Default Re: A problem with boat trailer lights

    old trailer.
    any rust is messing up the ground which IS the trailer.
    use an independent ground for every light

  17. #17
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    Default Re: A problem with boat trailer lights

    Quote Originally Posted by wizbang 13 View Post
    old trailer.
    any rust is messing up the ground which IS the trailer.
    use an independent ground for every light
    You can bet if you have a 12 volt problem that is not immediately obvious it is an earthing problem. A seperate earth wire the best solution to eliminate possible problems.

  18. #18
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    Default Re: A problem with boat trailer lights

    When I was pulling my trailer in and out all the time I gave up on hardwired lights and hung a piece of wood with lights mounted off the aft end of the boat. Never got wet, never got corroded. This was salt water so harder on fittings than fresh.
    Steve

    If you would have a good boat, be a good guy when you build her - honest, careful, patient, strong.
    H.A. Calahan

  19. #19
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    Default Re: A problem with boat trailer lights

    Poor ground #1 answer, I really like silicone grease in all plug in connections, especially in the salt.

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