What's going on here?

[Skunksmash]

I'm having a strange electrical problem. Well, it seems strange to me at least. I did the H4 headlight bulb conversion on my 87. Bought some better headlights off ebay, and wow what a difference in night time visibility. I used those Hella brand relays, that have a fuse in them. Put them up by the battery, so they'd be easy to deal with in the event that I ever needed to work on them or anything. As you can see, they're melting. Wouldn't a short that was capable of generating that kind of heat, blow the fuses?

But it hasn't. You can see that one fuse, has just completely melted. Well, the plastic has melted off of the fuse, anyway. But the metal is still there, and still functioning. This all seems pretty strange to me. That the fuse didn't blow. They're just 25 amp fuses, for these 25 amp relays. Used 18 gauge wire, to wire up the headlight conversion. So I don't think its anything to do with the wire diameter.