Hi,
I have a '97 F150 4x4 with an electrical issue with the trailer plug. this truck didn't have tow package,with only a 4 pin trailer plug at rear. I have added a brake controller and have installed the correct harness to tie it to main harness.
The trailer plug only has power on single pin for the running lights. No power for brake or turn signals lights.
I traced wiring from rear of truck to distribution box at front. No fuses blown. The wiring is not corroded at rear,as truck is mostly rustfree. I don't have a wiring schematic,that shows the trailer wiring.
Would appreciate anyones experiences with similar issue. thanx,Tom

 

I since I posted have found the reason why my trailer lights didn't work. I found a fuse for these lights under the hood. I didn't think this plug wiring was fused,but it is. Tom

 

That is good that you solved your problem by your self. At least you gain and learned additional knowledge which you cans share to others in the future. Welcome to the forum.