Trailer wiring

Discussion in 'Mechanic and Repair' started by A1 Grass, Oct 21, 2002.

  1. A1 Grass

    A1 Grass LawnSite Senior Member
    Posts: 330

    Having a problem with trailer light wiring.

    My truck was already wired up when I bought it (used). When I hook it up to the trailer the lights/signals work correctly, but flash faster than when NOT hooked up to the trailer. PLUS the fuse for the back-up lamps blows. Any ideas?
  2. parkmaster

    parkmaster LawnSite Member
    Posts: 68

    put a heavy duty flasher unit in place of the other one.

    you plant it, I'll maintain it
  3. sdwally

    sdwally LawnSite Senior Member
    Posts: 385

    They flash faster due to the change in resistance to the circut. A heavy duty flasher unit should correct this. Fuse blowing, sounds like a short in the trailer or plug is wired wrong.
  4. Alan

    Alan Member
    Posts: 1,185

    Somebody else already mentioned the increased load is what is making the flasher cycle faster.

    I assume you are running a 7 pole flat blade (RV style) connector. That being the case, the trucsk side is most likely wired correctly to give you backup lights on the trailer. But most trailer lack backup lights and it's pretty common for that same terminal in the trailer side to be wired as a ground. The trailer will also get ground through the ball, so when the backup circuit is energized it passes current through the trailer ground wire, through the trailer frame and back to the truck, equaling a dead short. Only way I know about that is because I delivered a boat with a trailer wired that way and lost both backup and turn signals.

    Lite-Mate wiring adapters used to come with a backup light wire in them and a seperate ground until it became obvious that so many trailers were wired wrong and the connectors were getting blamed for wiping out fuses.
  5. GarPA

    GarPA LawnSite Silver Member
    from PA
    Posts: 2,585

    just yesterday I had my first light problem with the trlr.,,,I cant seem to fix it. All I have is a right signal and stop light ...nothing else. I tested the plug coming off the truck and only one prong has juice. Crawled under the truck and it looks like since this was wired at the factory, the wires are tucked up under and behind the frame...yuck...any of you have any words of wisdom on how to fix it or what the problem may be? I hate to take it to the trlr dealer bcause I dont want to lose a days work right now...but this one might be something I cant fix?? thanks much
  6. hosejockey2002

    hosejockey2002 LawnSite Bronze Member
    Posts: 1,195

    Kitzy- If your truck has a factory tow package it might have separate circuits for the tow package. For example, I had a '94 F250 with separate fuses for the trailer circuits. So if you had blown trailer circuit fuses, the lights on your truck would still work, just not your trailer lights.
  7. ProMo

    ProMo LawnSite Bronze Member
    Posts: 1,468

    I had that problem there was another fuse panel under the hood

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