I'm going out of state soon and will be pulling a friends 24ft gooseneck flatbed from West Texas to Florida. All the lights and trailer brakes work when hooked up to his 05 3500 dodge cummins but when I hooked up on my 08 f350 powerstroke the lights don't work and a message saying "trailer disconnected" will appear as well as "wiring fault on trailer" I'm leaving in a week and really need some help. Thanks!

 

Lots of images to look at. I'd grab a voltmeter and step through all your truck connections. Check out this image of typical connection.

 

The first thing I would do is run down the ground for the truck adapter and clean it real good and then see how everything works.

 

Does the gooseneck hook up to the ground? My lights work just fine with a bumper pull 4 way hook up.

 

I've had issues with certain brand connectors. Push it in as hard as you can and make sure it's all the way in. If that makes it work you'll know. Like bubba said, check all the connectors. Is it still the factory 7 way?

 

Yes sir it is still the factory 7

 

The TBM is very sensitive to grounds. I would say that this problem is generally 90 percent of the time related to the ground not being sufficient
. The TBM sends small signals back and forth to verify the trailer is hooked up, the voltage is not much and so the ground has to be perfect.

On one truck we had to run a 10 gauge wire from the battery all the way to the back of the truck to insure a good ground. Its easy to check even if you mock up a ground wire to the plug from the outside of the truck and the trailer and retest it, if the problem goes away you just need to run a good ground, i honestly can't tell you how many times i have had to do this.

 

I would not automatically think that YOUR truck is the problem. There IS an industry standard for trailer tow wiring, connectors and connector pin location and usage. I do A LOT of trailer wiring diagnosis and repairs. On occasion I have a customer come in to the dealership with this very complaint. The problem is NEVER the truck (excluding blown fuses due to wiring faults in the trailer) and is usually caused by the trailer being wired to match another truck, probably incorrectly wired as well. I have heard on more than one occasion that some fleets and construction companies for example, PURPOSEFULLY , and purposely , wire their trailers differently to make theft a little more difficult. This is all fine and dandy, until you introduce a new truck or trailer to the scenario... in comes you and your truck for example. You stated that the lights do not work, and there are trailer brake and wiring fault warnings in your message center - this indicates there is more than a ground problem.

There are inexpensive trailer wiring tester tools that will help you easily test the trailer wiring. For a little more money you can buy one that also has a trailer brake simulator built in that will allow you to verify that your electric trailer brake actuator is also functioning. I use the Tekonsha 6562 7-Way Blade Tester and Trailer Emulator w/LED Display on all Ford applications with or without the integrated trailer brake control. These are a little more expensive and you don't necessarily need the brake emulator if you just want to verify your lighting circuits.

See product here: http://www.tekonsha.com/products/ele...9vgARQnbu7ZwgF