Trailer Not Recognized with Brake Controller

Discussion in 'Trucks and Trailers' started by Mack77, Apr 26, 2010.

  1. Mack77

    Mack77 LawnSite Member
    from NJ
    Messages: 212

    I have the P3 brake controller, and looking to tow a trailer I purchased used with 4 drum brakes. It's all wired up, but the controller is not recognizing a trailer is connected.

    I purchased the OEM wiring harness that clips into the factory wiring, connected the trailer and nothing happens. Am I missing something?

    (This is my first time connecting a trailer with brakes.)


    CLARK LAWN LawnSite Silver Member
    Messages: 2,526

    do you have power at the plug at the rear of the truck? these are very simple to wire. if all good in the truck side then start checking all you connections on the trailer.
  3. Mack77

    Mack77 LawnSite Member
    from NJ
    Messages: 212

    All I have is the plug connected under the dash and the 7-pin OEM hitch set up at the rear of the truck. Do I need a separate battery on the trailer to get the brakes to work, or is power drawn from the tow vehicle?

    All lights work, turn signals, brake lights, etc. Just no power to the breaks.

    The trailer also has a break away kit, how do these work?
  4. kps2389

    kps2389 LawnSite Senior Member
    Messages: 346

    Make sure you have the brake controller wired correctly. When I put the break controller in my truck I just matched the wire colors from the controller to the factory plug and harness. It ended up being wrong the colors were different. As for the break away system you need to hook the cable on the safety chain and if the coupler comes off the ball it will plug out the plug and lock up the brakes.

    CLARK LAWN LawnSite Silver Member
    Messages: 2,526

    in the 7 pin plug you should have three posts that are hot when you hit the brakes. the two for the turn signals and one for the brakes. the one for the brakes will get bright and dim on a test light when you move the power dial up and down.
  6. igotdiesel2

    igotdiesel2 LawnSite Member
    Messages: 135

    On the truck side take a volt meter and find a good ground on the truck then find the pin in the connector that controls the brakes, Have someone hit the controller and see what your reading is on the volt meter. If it is close to the number on your controller it is in the trailer. You can get in the plug of the trailer find the brake wire and see if it is connected. Also you can take that wire off and run a jumper to the POS side12v battery and then run a wire from the NEG to the trailer frame. If you hear buzzing at the wheels then the brakes are good and you need to look at the truck for the problem. If you don't hear a buzz then you have a broken wire somewhere on the trailer. The FIRST thing I look for in any kind of trailer electrical problem is the ground from the truck to the trailer, make sure you connect the ground through the plug and not the hitch ball combo. It is a much better, sound connection. I know this was kinda long, but I hope it helps. -Jason
  7. spunkmeyer

    spunkmeyer LawnSite Member
    Messages: 2

    When I hooked up a brake controller in my 2002 Silverado I had to install a fuse and connect a wire that was in the battery box but not connected to anything, even though the truck had the towing package and came with the chevy pigtail for trailer brakes. Like igotdiesel2 said, pull out your volt meter.
  8. PTSolutions

    PTSolutions LawnSite Silver Member
    from OH
    Messages: 2,331

    yea, i just installed a P3 in our 02 2500HD. if the truck came with the tow package, you just need to put the harness in the correct spot under the dash (theres like 3 options) and make sure u put the 40amp fuse in the panel under the hood.

    i checked to make sure i matched the wires up correctly like 3 times, dont go by colors, there should be a tag on the harness that tells you which wire is which, then hook them together.
  9. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    Some brake controllers have a switch for different configurations,
    flipping this switch might get them to working?

    It's usually on the back end...
    If yours has it.

Share This Page