The problem could be as simple as bad connections right at the fuse, IE bad fuse, bad fuse clips, poor connection between the fuse clips and the terminals in the back of the fuse box, and of course bad / corroded/ loose connections right at the wires
In addition to other posts above, you need to find out what is REALLY (actually) supplied from that fuse. Measure the current draw with a multimeter. This is easy to do. Get an inline fuse, same rating as whats in the box and remove the fuse from the box. get some good alligator clips and clip onto the fuse holder
Wire it From fuse clip.............to temporary inline fuse.........to multimeter........through the meter...........to remaining fuse clip
Carefully set your meter up for amperage and see what it draws.
Your factory service manual has a chart somewhere near the wiring diagram section showing what loads are on that fuse.
