Does anyone have the diagram for the truck end of the factory 4 pin trailer connector? I am installing a 4 to 7 pin adapter and the lights all work but the blue wire which should be the brake signal does not connect to anything in the the truck side connector. There are 2 blue wires on the other side (truck itself) which don't connect to anything in the connector either. I have an adapter for my Prodigy to plug in to the factory harness but I can't figure out where the brake wire is at the back of the truck. Help anyone!

 

The flat 4 style does not have a brake function. If you are adapting from flat 4 to 7 way round you won't have a brake wire. Did your truck not come with a 7 way round from the factory? I think the flat 4 just has left turn, right turn, tail light, and ground.

 

The 4 wire has the extra wires taped up, blue and red. The red is 12V ignition and the blue I assumed would go to the factory brake controller plug. I've tried to trace the wire from the brake controller side but it goes way too deep in the dash for that. I know I could just run a wire from the controller to the plug but I can't help but wonder where the blue from the controller ends.

 

Blue is definitely brakes. The red should be the 12v for charging trailer batteries. On mine I had to plug the harness under the bed into the trailer connector. Can you find where the connector is plugged into the harness? I also had to install some fuses/relays under the hood if I remember correctly. It was a few years ago. All of the items were in the glovebox with factory instructions.

 

I bought the truck used so none of the factory instructions are there. My main question is where does the blue wire from the brake controller plug under the dash go? It's doesn't appear to be at the back of the truck. There were holes where someone had a brake controller installed previously so it must be there somewhere but I just can't find it. I have checked all the fuses and relays, everything there looks good. I do have power to the brake controller.

 

What did you plug the brake control into? I had a harness that plugged in under the dash that had the pigtail for the control on the other end. The blue wire should more or less go from the brake output on the control to the back of the truck where you are seeing it.

 

I found my Ford instructions for setting up trailer wiring. Inside the large access panel under the steering wheel on the right side you will find the connector for the brake control install. It will have six wires: red, light green, dark blue, white and brown. Those wires should be going to your control. Red is 12v, light green is brake switch feed, dark blue is brake output from control, white is ground and brown is illumination.
You should also have a 30a fuse in cavity 28 in the power distribution block underhood next to the master cylinder.
I don't have a scanner, otherwise I would send it to you.

 

Yeah, I found the connector under the dash. The problem I was having was finding the brake signal at the back of the truck. I stopped by the local dealer yesterday and they helped me find it. What happened was the output control on my brake controller got turned down to 0 by accident and I wasn't getting a signal because of that. But the connector that adapts the 4 wire trailer connector to the factory harness doesn't match its blue wire to the factory blue wire. It looks like a factory adapter but it just doesn't have that one pin in the right place.

Thanks for the help though. Some of this info is really hard to dig up. The dealer mechanic took about 30 min. digging through diagrams on the computer to find what I was looking for. The service mgr didn't really seem to have a clue.