I currently have a 2001 F-150, that blows number 113 fuse (which is a 40 amp fuse) in the power distrubution panel under the hood.
This fuse is identified as "Ignition switch battery feed - run and accessory circuits."
No other fusues blow.

 

In which key switch position does it blow, RUN or ACCY?

 

We found it, the wires harness near the brake pedal arm had a bare spot and was making contact. Which was blowing the fuse.