Funny enough i was reading this type of problem the other day on the DML, I have reposted this here. As has already been said nice clean contacts are essential and if you do have to replace with an in line fuse holder get a correctly rated 'quality' one.
I quite like the look of those modular relay / fuse racks that can be bought nowadays.
http://www.vehicle-wiring-products.co.u ... elays.html
Modular fuse and relay housing system.
Quote:-
The blades of those 'hard candy' fuses are aluminum. They will develop
an oxide coating fairly quickly. Normally, this is good because the
coating protects the rest of the piece from deterioration, which iron
oxide does not. When aluminum is used in electical applications, this
causes a problem because aluminum oxide does not conduct nearly as well
as metallic aluminum itself. The oxide causes resistance at the
connection. Resistance equals heat. We see, then, the phenomenon of a
fuse position melting apart with the fuse still intact. The remedy is
to clean, or better, change the fuses regularly. The fuel pump runs
through fuse #7. This means very high current in this circuit all the
time the engine is running. As the fuse blades oxidize, the resistance,
and therefore the heat increases. Soon enough, what ever holds the
fuse, well-fuses.
If you want to replace the fuse holder, you should be able to get one at
a good parts house, NAPA say. If you want to replace the fuse box, we
have new ones
Warren at DMC