My fuse block melted down too.
The fuse block melted and obliterated three fuses.
The problem seems to be corrosion on the non-copper (some cheap alloy) fuse contacts in the fuse block.
When the cooling fans come on, such as when the A/C is on, there is like 18 amps going across a 20 amp fuse. The current is below the fuse rating, so the fuse doesn't blow. But the knife-edge of the contact against the blade of the fuse is a small contact point, and it heats up and burns, especially if some corrosion builds up. Then it burns, but the plastic doesn't really support combustion, so once the current welding on the fuse blade stops adding heat to the fire, the fire puts itselft out.
All of this happening on top of the battery, which from time to time burps explosive hydrogen gass...
I replaced the fuse block, and use a dab of Kopr-Kote anti-seize compound on each fuse blade as a contact improver and corrosion preventer. No problems since then, 220,000 kms ago.
Mathew Banack
81 Rabbit Pickup LX diesel
98 Beetle TDI
03 Jetta Wagon (wife's)
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