Truck Repair: Fuses for trailer wiring 1998 Ford F-150, ford f 150, factory wiring harness

Question
Van,
 I need to know where the fuses are for the trailer lights (factory wiring harness), on a 1998 Ford F-150.
I dont have the manual for the truck and the dealerships dont know either.
Please help I have running lights but no turn or brake lights (trailer only).
I found 1 (one) 20a fuse under the hood that was blown but I dont think that is it. I looked under the dash fuse box, and under the hood on drivers side fender well has 2 (two) fuse boxes and 1 (one) relay box. All the fuses wher good,as far as I could tell.

HELP

Answer
Hi David,
The owners manual should tell you, but I believe it uses the same fuse as the truck lights.
Check the wire harness connections, and make sure a good ground runs through the plug. Don't depend on the ball fo electrical connection of ground. That's the most common cause of all those blinking trailer lights you see, especially on stock trailers.
Check the plug with a test light.
Van