It's either Fuse 29 or 30 for "turning on" the alt.
I had this same problem, fuse was visually good, but the fuse socket was worn out. I had to physically bend the fuse a little to get good connection. Someone had used a fuse tap on the fuse block under the dash and bent up the fuse socket.
I went through 3 alternators before I figured out that my fuse connection was intermittent.