The 2000 Ford Excursion doesn't have a fuse for the alternator in the traditional sense. The alternator is a high-current device, and its protection comes from the internal regulator and the wiring itself, not a replaceable fuse. Problems with the alternator usually manifest as a faulty alternator itself (requiring replacement) or a problem with the charging system wiring (which might involve a fusible link, but not a standard fuse).
If you're having charging problems, you should have the alternator and the entire charging system (battery, battery cables, wiring) checked by a mechanic. They'll be able to diagnose the issue properly.
