Here's the situation. As my sig indicates I have an F350, 2003 7.3 diesel. Factory trailer plug on the bumper.

I installed a Tekonsha P3 about three months ago using the Ford custom plug to the P3. No problems with the install. Backed it up to my new 7 x 14 enclosed trailer and tested it out-everything was fine, no warnings from the P3.

I recently purchased a used construction trailer for my business. The guy pulling it was using a 2004 F350, factory plug, with diesel. He had either a Valley or Hopkins brake controller.

I hooked the trailer up to my truck to bring it home and the brake controller instantly warned "overload-no trailer brakes" on the first brake input. I kept on since it was unloaded. Also, no brake lights or turn sigs.
However, the brakes actually do engage-you can hear them click in/out and feel the braking of the trailer brakes. At times, when tapping on the brakes, you can see the output power on the P3 rising up to different levels and then go overload. You can also get overload even when not engaging the brakes.

I feathered the emergency actuator underneath the controller to test the brakes independently of the truck brake input and does indeed engage the brakes.

Short somewhere maybe, harness, brakes on trailer wheels? Thoughts?

 

I would go through the wiring and make sure it is up to snuff first. If the lights don't work that doesn't say much for the rest of the wiring. I'd start there and see if there are any corroded connections for the brakes. you might find when the wiring is good for everything the error goes away. It might also be the magnets on the trailer require more current because they are getting old as well.

 

Start with the plug...most issues start and end there.

Good Luck,
Bill

 

After you've checked the plug, do verify that the "used" construction trailer still has a good ground wire. Grounding failures can cause all kinds of problems with the brake controller electronics - even causing it to burn up while "chasing" floating grounds as you're driving along.....

 

I get these calls all the time, except ours brake controller displays the high amperage. You definately have bare wire touching metal somewhere. If you get the overload message when the trailer isn't hooked up, the problem is in the truck somewhere. Chances are, it's the 7-way or the connections right at the brake magnets, just inside the wheels.

 

If there's a short it wouldn't affect the brake signal, but if there's a short AND a bad ground all of the above applies.

Construction trailers are among the most abused and neglected trailers imaginable - so I would not be a bit suprised if the wiring on it was a complete rats nest. There's also a good chance the light bulbs are all burnt out and were never replaced, checking them will reveal any bad sockets as well.