I have an 02 F-150 Lariat FX4 and for some reason my trailer brakes are not working. Help. I've wired up trailer brakes twice before on older vehicles, so I have some sort of experience with this.

So far, what I've done:

1. Installed new brake controller and used the simple plug in harness instead of splicing the wires under the dash. Seems to be working properly. All lights on unit work and light up when I press the brake pedal.
2. Wired a new harness on the back of the truck for the trailer to plug into. All lights work.

Not exactly sure why the brakes are not getting any power. I read somewhere that there is suposed to be a relay installed to get everything to work, but I think they are all there. The only relay not there is #302 under the hood that deals with "trailer battery charging". Could this be the culprit?

 

I know on mine I have a fuse.

 

I checked all the fuses and relays that are there. They are all fine. I'm going to go to the auto parts store tomorrow and get the relay that I think I may be missing. It's part # is FOAB-14B192-AA . The spot on the fuse panel where I'm going to put it is related to the trailer battery charging. Does not sound like it is the problem, but at this point I'll try it.

Also, is there a 3rd fuse panel?

 

Well, it was that dang relay. If anyone else has problems setting up their trailer brakes the relay is in spot #302 under the hood. It says "trailer battery", but the brakes will not work either without it. You would think Ford would put that in their description in the manual.

 

It is in the manual kinda... Its like a puzzle. I didn't realize it was in there till a thread like this popped up and one of the awesome people that are here posted up some manual pages. Picked up the full ISO relay and the trailer braking system has been good since then.

 

Thanks to this thread and Site i found out where the relay went in my 2008 . Mine is Relay #05 (trailer tow battery charge in the fuze panel passenger side.