89 camry fusable link

got an '89 camry with a destroyed 80 amp ALT fusable link located at the battery. I know how to remove it,, but what could cause it to fuse? Any suggestions on what to check before I replace the broken one?

Looking at a skimpy Haynes manual schematic it looks like anything on the "B" circuit. First and foremost that would be the alternator. Beyond that the ignition circuit, taillights, stop lights, A/C and heater, defog, and interior lights. Go to Autozone.com for schematics and info.
Just to CYA make sure the battery isn't shorted since the biggest fuselink went. Wow. I've never seen one go. Let us know what you find.