As exranger06 stated, the first thing you need is a wiring diagram. You need to find out what other circuits does that fuse feed. I would also get a multimeter and a test light. Once you figure out what circuits are on that fuse, do a visual check. Heat and vibration are two big culprits in electrical issues and check any wiring that is close to either. Bad grounds are also a place to look at.
Good luck, electrical issues can be frustrating.
Good luck, electrical issues can be frustrating.