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ground wire question

Discussion in 'Trucks and Trailers' started by Keegan, Jul 8, 2013.

  1. Keegan

    Keegan LawnSite Senior Member
    from CT
    Messages: 608

    The lights on my trailer stopped working. I replaced the lights. I'm assuming it's the ground because I hooked the trailer up to another vehicle and it didn't work on that either so it's not my truck.

    I looked on my ground and it's screwed to very rusty metal. Could that be the problem? I didn't see any breaks in the wire.

  2. Dually00-00

    Dually00-00 LawnSite Member
    Messages: 181

    A cheap test light or continuity tester would take all the guess work out of it. Check all your connections in trailer plug and tow vehicle . Check your fuses too.:waving:

    CLARK LAWN LawnSite Silver Member
    Messages: 2,526

    Do you have a DMM? Ohm the ground wire from the ground pin on a light pigtail to the ground post on the trailer plug. Should be less than 4 ohms. Have you made sure that you have power to them? Could have a bad wire in the plug.
    Posted via Mobile Device
  4. Keegan

    Keegan LawnSite Senior Member
    from CT
    Messages: 608

    I changed the two back lights and now they only work on turn signaling and braking but not when the lights are just on. I joined the wire colors exactly the way they came off. What did I do wrong?
  5. kgs1

    kgs1 LawnSite Member
    Messages: 146

    start with cleaning that ground up then check again...using a simple test light will do the job... then,test truck side first at pigtail & make sure everything is good there...then, plug trailer in & take lenses off trailer lights...make sure your bulbs are good...take bulbs out & test with test light where bulbs make connection...do one side at a time; brake/l-trn/r-trn/running lights...see whats working & whats not...if none are working at all then strart with that ground where its connected to trailer....
  6. kgs1

    kgs1 LawnSite Member
    Messages: 146

    check it over again, look on back side of your new lights..it will tell you where to put wire for the running lights & also for the brake/turn lights.. if you have one & not the other working then check with test light at the trailer light without the bulb in....were your wires spliced before?? if so check there for power to each wire & your turn & brake are on the same wire & running light on the other...

    CLARK LAWN LawnSite Silver Member
    Messages: 2,526

    Check for power in the brown wire with the marker lights on. If you have power the use a DMM and check for continuity between the pin for the marker light and the ground.
    Posted via Mobile Device
  8. herler

    herler LawnSite Fanatic
    Messages: 5,141

    The first step I always perform is to make sure power is getting TO the connector.
    Granted the fault is usually in the trailer but not always.
    While test lights certainly are required, I like to have some of these handy:


    Once I KNOW that power is getting TO the connector, I then proceed with the trailer's wiring.

    Otherwise it's just no use, how do I know where the fault lies.
  9. 70marlin

    70marlin LawnSite Member
    Messages: 29

    I always pull a separate ground wire for the trailer lights. Frame grounds always corrode and fail. Use high grade connectors and dielectric grease and heat shrink tubing secure the wiring harness to the trailer. It should last a long time and when they do fail, most of the time its lamps or the tow vehicle harness not the grounds. I recommended http://www.amazon.com/s/?ie=UTF8&keywords=powerprobe+iii&tag=googhydr-20&index=aps&hvadid=30066605867&hvpos=1t1&hvexid=&hvnetw=g&hvrand=704143000648362954&hvpone=&hvptwo=&hvqmt=b&hvdev=c&ref=pd_sl_8zo9rlnmoq_b the power probe 3 for test equipment. it does so much more than continuity.
  10. dieselss

    dieselss LawnSite Bronze Member
    Messages: 1,898

    Always gnd every light. Pwr and gnd. If you main gnd is nasty and rusty your not getting gnd signal. When you put you new lights on...how did you gnd them?

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