Weird trailer lights

Discussion in 'Mechanic and Repair' started by cariboulou, Jul 28, 2005.

  1. cariboulou

    cariboulou LawnSite Member
    Posts: 160

    When I use right turn signal, both lights on trailer flash on and off. When I use left turn signal and parking lights the flasher stops and remains on and doesnt blink. any ideas? thanks in advance
  2. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    Sounds like a bad ground, Clean the trailer ground wire connection and the plug ground on your truck or car, If that doesn't do it check the bulb sockets on the trailer for corrosion,That could cause a feedback to the flasher also.
  3. MowerMedic77

    MowerMedic77 LawnSite Bronze Member
    Posts: 1,164

    Is this a new truck and old trailer or the other way around or is this a new issue with existing truck and trailer? :dizzy: Gunna need more info,To try and help.
  4. PTP

    PTP LawnSite Bronze Member
    from Tulsa
    Posts: 1,383

    When I bought my new trailer, I already had a wiring harness on the truck. I plugged it into the trailer and had symptoms like you are describing. I got a new harness and the problem was fixed.

    Trailer wiring is simple. You need to figure out what wire from the truck is supposed to cause what light to come on. A simple test light will tell you. Then trace the wire that it connects to on the trailer and see which light it goes to. If it goes to the wrong light, you can cut the wires by the harness and splice them to the correct wires.
  5. fixer67

    fixer67 LawnSite Silver Member
    Posts: 2,100

    You are not trying to ground thought the trailer hitch ball are you? I seen that tried some many times I have lost count. You must run a wire thought the plug from truck to trailer for ground. It sounds to me like that best thing to to is just cut the plug off the trailer and rewire the plug to match the trailer-truck set up you have. You will waste 10 times more time trying to find the problem than it will take to just rewire it. When I get a old mower in the shop that has been rewired a dozen time that does not work right I just get out the wire cutters and cut all the wires out and start over. I can build a new harness in a lot less time than it would take to find the problem.
  6. cariboulou

    cariboulou LawnSite Member
    Posts: 160

    used a test lite and it works as normal when turn signals are on. but when i hook up trailer problems happen. I rewired ground to trailer again same spot but cleaned up with a wire brush and same thing. even tried changing bulbs..but no luck. Will check the ground on truck tomorow, its an 02 f150 with factory tow pkg and wiring harness. the ground for the trailer is the the frame of the trailer with a 2" tek screw through the steel. the trailer is an ew model as well, as 04 bray single axle.
  7. CCWKen

    CCWKen LawnSite Member
    Posts: 113

    The standard for trailers is:

    Yellow - Left Turn/Brake
    Green - Right Turn/Brake
    Brown - Park/Clearance
    White - Ground

    Check the output from the truck to the matching pins of the trailer.

    Check for pinched or chaffed wires (grounded out) where wires may be held to the trailer frame with clips.

    Check the individual light grounds. Bolts and/or wires may be corroded.
  8. jt5019

    jt5019 LawnSite Bronze Member
    Posts: 1,432

    I had almost the same problem it turned out to be one of the wires going into the back of the left trailer light.Somehow it was pulled out just a tad causing a bad connection.

    SHOWCASE LAWNS LLC LawnSite Member
    Posts: 238

    Definitely A Ground Issue. If The Truck Doesnt Have The Problem When The Trailer Is Off The Its In The Wire Harness Or One Side Of The Truck/trailer Connectors . Sometimes On The Trailer Its Faster To Just Go Get A New Spool Of Trailer Wire And Redo The Wiring On The Trailer From Scratch.
  10. fixer67

    fixer67 LawnSite Silver Member
    Posts: 2,100

    I just remembered a mistake a man across the hill made a few years back on his car. His lights went nuts on him. He had by mistake put a 1156 (single contact) bulb in a socket for a 1157 (double contact) bulb. It was causing a cross short between his running light and his brake and turn signals. Just check to be sure the right bulb are in the right sockets. The two bulbs , 1156 and 1157 have locking pins on the sides of the bulbs to help prevent this type of mis-match but it still can happen.

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