Trailer lights

Discussion in 'Shop Talk' started by Rowdy, Jul 21, 2005.

  1. Rowdy

    Rowdy Well-Known Member

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    Jul 9, 2004
    Location:
    Jones Co, Texas
    Well, I wired some new light on a trailer I just bought...

    Here's the problem :help: :p

    Everything works until the running lights are on. If the brakes are applied with the running lights on, both tail lights go dark. The blinkers will work with the running lights, but the braklight will not work with the running lights.

    I suspect that the problem is in the grounding. It seems like almost every mystery problem in a 12 Volt system ends up being something to do with the ground. I used the exisiting ground on the trailer, just spliced into it. Tomorrow I will unbolt it and use a wire brush. The tailight housings also ground to the frame, so I will clean those up as well. I'm not real confident about this, but it is a start.

    It has been quite a few years since I have wired a trailer, so for review here is how I have it done:

    Brown wire to each brake lamp's black wire.
    Green wire to right light, hooked to the red wire.
    Yellow wire to left light, hooked to the red wire.
    White wire spliced into wire that is grounded underneat a bolt in the trailer frame. I did not mess with bolt, so ground may be corroded.

    All colored wires have power. All wires pass continuity test conducted from trailer pig tail. (ie white to brown, white to green, etc....) So, that doesn't really support my grounding idea, but perhaps it is a weak ground.

    It could be the truck wiring, but I did hook the trailer up to another truck, and it did the same thing. So either the problem is in the trailer, or the two trucks have the same problem.


    Anyway, any help for me? Am I missing something simple?

    Rowdy
     
  2. mohillbilly

    mohillbilly Well-Known Member

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    Mar 24, 2005
    Location:
    south west Mo
    you are right. always make sure the ground is good, that is usually the problem 75% of the time. The ball hitch (if you are using one) is not the best method to conduct electricity, A seperate ground wire/plug is the way to go
     

  3. rambler

    rambler Well-Known Member Supporter

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    MN
    The other issue would be current draw on thinish wires. how many running lights did you install?

    --->Paul
     
  4. moopups

    moopups In Remembrance

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    In beautiful downtown Sticks, near Belleview, Fl.
    Your wireing colors are standard and correct, the problem might lie within the trucks wireing harnesses. Are they older American models or newer imports? The Europian wireing system takes an adaptor, if the directional lights are amber with the run/stop light seperate and red, then you need the adaptor. Establish that the power is propperly being sent first before changing the trailer's wires. The adaptors are about $20.00 at any parts store.
     
  5. Grizz

    Grizz Well-Known Member

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    May 11, 2002
    Location:
    south central pa And northeast Fl
    Trailer wiring is Brown is TAIL And Marker
    Yellow is LEFT turn
    Green is Right turn
    White is Ground
    brake lites work trew the turn signals

    U MUST wire up a ground it wont ground properly trew the hitch ball

    How do i know this 30 years of building and sellin trailers
     
  6. Rowdy

    Rowdy Well-Known Member

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    Jul 9, 2004
    Location:
    Jones Co, Texas
    Okay a few more details.

    The truck is a 1977 f 250.

    The only lights on the trailer are the two Tail lights on the back. The one above the licence plate has a clear lens pointing down to light the plates. Each tail light only has one lamp, but it is a 1157 which has two filiaments.
    I did run a ground wire, but it could still be the ground, since the wire is grounded underneat a rusty nut, but it is ground enough for most of the system to work...
    The wires are either 14ga or 16ga. I don't have the trailer with me to check, but the trailer is only 10 ft long, so the wire size should be enough.

    I'm going to pull out the multimeter and test the vehicle side to be sure everything is right in the pigtail of the truck.

    Thanks,

    Rowdy
     
  7. Blu3duk

    Blu3duk Well-Known Member

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    Location:
    central idaho republic
    Ive had the same problem with my 77 fords when trailering.... solution was to add a ground wire from the frame of the truck back to the tongue of the triler, and another solution for one triler was to actually cut into the wiring harness of the ford on each side and pigtailed the wires out at the taillight lens and kinda hard wire the trailer to the truck with wire nuts.... [got rid of that trailer after a couple years.....

    Some folks never have a problem with grounding on their old 77's, both of mine have problems, one manufactured October 76, the other June 77 so it wasnt a common type same run problem.... my 78 doesnt have that problem, but I still run an extra ground wire from the frame just the same to be sure....

    William
     
  8. gardentalk

    gardentalk Well-Known Member

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    Ever heard of Hooked On Phonics? ;)