Hey, quit confusing the guy I was helping!
First off, that strip fuse is for the blower motor, not the aux fan. Secondly, intermittent operation is
quite common with these strip fuses because they develop a tiny crack at the thinnest part of the fuse, which, depending on temperature, will either make contact or not. A very typical failure, I have had it happen to me 3 times.
While there may be another cause in his case, this is absolutely the first thing he should check.
The lid has a tiny latch on the side that has to be pried slightly, then the thing will open right up. Just dig your fingernail or a flat object under the lip of the latch and lift up. Look for corrosion (usually whitish) and/or a crack right in the middle of the fuse where it is thinnest.