fusible link??

[Hank70SS]

Is that feeding the interior via the bulkhead connector? If so a 20 amp fast blow isn't going to cut it. Look at the fuses in the fuse block, add them up and it's a lot more than 20 amps. Now you shouldn't be pushing them all to the limit but you could easily exceed 20 amps. There should be a 16 gauge fusible link wire from the horn relay to the main splice in the harness, that feeds the fuse block. There should also be a 14 gauge fusible link wire between the battery positive post and the junction block on the rad support.

Unlike a fuse a fusible link wire can withstand a momentary direct short or temporary overload without blowing. Unless you've added high current draw accessories to the interior I would reinstall the fusible link wire and get rid of the fuse.