I think you have a bad connection at the fuse, which is causing arcing, which (in-turn) is melting the fuse and connector. You may want to run dielectric grease in that fuse holder as well.

 

Yeah, I replaced the fuse holder to one I got from advanced auto with a brand name fuse in it as well. I think what your saying could have been the issue. but no problems thus far *crosses fingers*

 

bumppppp. I had this same issue..turns out the soldered wire connection before the fuse fell apart after two years and the electricity was running through only a few copper wires that were still making contact. Mine completely melted just like this so it must have gotten HOT. I cut back the wire and soldered a new inline fuse in but nothing is happening. Relay clicks and I have power at the fan connector. Think the fan motor blew when this happened?

 

Soldering a relatively high amperage connection isn't always the best solution. If anything happens, such as a cold solder joint for example, you will end up with a hot connection that can end up melting the little bit of solder that holds things together. A crimp or a screw-down is a much better solution, and in place of devices such as relays, a better approach is a "solid state switch".

If you're not sure about the electric fan motor, try hooking it up directly to the battery to see if it starts.