utility trailer wiring ?

Discussion in 'Shop Talk' started by WIPPdriver, Dec 12, 2004.

  1. WIPPdriver

    WIPPdriver Well-Known Member

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    Okay hears the deal.
    I have a flat bed trailer that has brakes at all four corners. I have a problem with the brake controller and the right turn signal. When I apply the brake pedal the trailer brakes lockup(REALLY LOCKUP) and when I turn on the right turn signal the trailer brakes will apply in conjunction with the turn signal. When inside the cab with right turn signal on and when I apply the brake pedal I can hear the turn signal flasher buzz. On the controller the green light is on until I apply the pedal, then it will go out and the red light doesn't come on. I have chased the wiring on the trailer and truck and can't find anything wrong.
    Green - right turn
    Yellow - left turn
    brown - trailer marker
    white - ground
    blue - brake
    black/red - aux.
    Thanks in advance!!
    Marlin
     
  2. agmantoo

    agmantoo agmantoo Supporter

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    do you have a wire ground from the trailer to the tow vehicle? If so, do you have a clean connection on the trailer and the tow vehicle or is the connection rusty? What type of connector do you have to connect the tow to the trailer? Here is a diagram of a couple typical connectors
    http://www.chuckschevytruckpages.com/trailerlights.html
     

  3. uncle Will in In.

    uncle Will in In. Well-Known Member Supporter

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    I had that problem with a stock trailer. The right turn signal would lock and release the brakes. The cause for my problem was a loose wire in the big trailer plug. Slip the cover off the female plug and see that all the wires are in their proper place with no stray wires crossing over to another screw.
     
  4. agmantoo

    agmantoo agmantoo Supporter

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    I believe the 6 wire drawing here http://www.etrailer.com/faq/wiring.asp is what you have. Compare each half of the connector shown here as to the method you have the tow vehicle and the trailer wired. It is easy to get wires in the wrong place.
    Wiring is not standardized and some trailers require the power to come in the center lead and on others center lead may be brakes.
     
  5. WIPPdriver

    WIPPdriver Well-Known Member

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    Well fellas, I have done everything. I have looked at the ground, loose wiring, crossed wiring, corroded connections, etc. I did this before asking for help. I still am having trouble. I'll try some more in the morning. Thanks.
     
  6. BobBoyce

    BobBoyce Well-Known Member

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    Sounds to me like the socket on your truck is wired for one configuration, and the plug on your trailer is wired for a different configuration. If that is not the case, then I would suspect a faulty or miswired brake controller.

    Bob
     
  7. uncle Will in In.

    uncle Will in In. Well-Known Member Supporter

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    The color of the truck wires usualy don't match the color of the wires in the trailer cable. Use a tester to be sure the truck wires are what is called for in the trailer plug.
     
  8. ed/IL

    ed/IL Well-Known Member

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    Has this setup worked in the past or is this a new rig?
     
  9. ed/IL

    ed/IL Well-Known Member

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    The first thing I would do is find out if trouble is in truck or trailer. I think they sell a test light that plugs in and trouble shoots for you. You also could use circut test light and test brake terminal with turn signal on. Test turn signal with brakes on etc. If you know someone with same set up hook their truck to your trailer or your truck to their trailer. Pain in the neck to figure out but once you do new problems will probably be easy to fix. My guess is plug at truck or plug at trailer.
     
  10. reitenger

    reitenger Well-Known Member

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    Where are you located? If you are located close enough to me. I can help you out. Also what vehicle are you hooking this to? Newwer Fords that have the prewire harness under the dash for the brake controller have a matching plug under the dash that will do exactly what you are saying if you use it. Nothing else, hook someone elses truck up to the trailer to isolate the problem to the trailer. It is most likely a wire touching inside of one of the plug heads.
     
  11. John Hill

    John Hill Grand Master

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    Sure sounds like a mixup in the wires. You mention that pushing the brake causes the trailer brakes to go full on.

    It is my understanding that the electric brake unit has a 12 volt supply lead and a control lead. Possibly that control lead is being brought to either ground or full 12 volts to cause the lockup.

    Is it possible that the wire for the 'stop lights' has been connected to the connection for the brake unit? Possibly through confusion with 'brake' as in 'brake unit' and 'brake' as in 'brake' light?

    The problem could be crossed over wires in the trailer or the truck, not necessarily errors, just to a different plan.

    Also, ensure trailer light fittings are properly grounded to the trailer chassis and the trailer chassis is properly grounded to the truck. If there is a bad connection there the ground current from the stop lights will try to return to the truck via other lights and circuits causing real head scratching problems.


    My suggestion is to methodically work through the connections until you get them sorted. This is what I would do:

    Get a short lead with a 12v lamp on it, a pencil and notebook and for comfort a low stool. Take a seat near the trucks trailer socket and connect one lead of your light to the truck ground.

    Work through all the connectors on the truck socket and write down any that are live, there may be none.

    Turn on truck lights, and work through again until you find the connector that has come alive, obviously this is the tail light connector. Turn off truck lights.

    Use a piece of wood or a helper to hold the brake pedal down, check until you find the stop light connector. Maybe you will find more than one that has come alive, if so then one might be the trail brake control line.

    Release the brake pedal, turn on ignition, check for new 'live' connectors, these could be accessory or supply to the trailer brakes but only if the trailer brakes only work when then ignition is on.

    Select right turn and find the connector that has the flashing signal on it. Do the same for the other side.


    Turn the ignition off.

    By this time there will not be many wires left! You should have a nice list in your notebook of all the connections as they are wired on the truck.

    Now bring the trailer up close to the truck but do not connect the cable.

    Make a connection between the ground of the truck and the ground of the trailer.

    Connect a wire to the truck connector you know is for the tail lights, turn the truck lights to park. What you have now is a live 12v lead to investigate the trailer wiring.

    Using this wire probe the plug on the trailer to identify the tail lights, the stop lights, the turn signals. You might need a helper if you cant see the back of the trailer while you do this and write your findings in the notebook.


    Turn off the truck lights and carefully study the list you made of plug and socket. If the truck is not wired the same as the trailer it should show when you do this.

    If there are faults in the trailer wiring, such as wires touching, that should have showed too.

    I hope this is useful to you.


    John
     
  12. John Hill

    John Hill Grand Master

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    Ooops! One bit does not read too well! When you come to check the trailer connection use your test lead with the lamp as the lead between the hot connector on the truck and the various points on the trailer. Use the highest wattage bulb you can for your test lead, if you use a low wattage bulb there may not be enough current to make the lights at the rear of the trailer obvious.

    They way I initially described it could give you a short to ground if you used a plain wire and touched a grounded part of the trailer.

    Sorry about that.
     
  13. jefferson

    jefferson fuzzball in the Cascades

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    Is your truck a newer model, while the trailer is older than dirt? ie; trucks now use the Europe type system. Lots of trailers out there still have US wiring, brake and turn on same bulb.