help with the fusible link wire smoking under the dash as i drive

like the title states. i can leave the key in the on position for days, with no smoke from the wire, but when i drive the car down the road, i get that aweful smell of burning wire. i feel all the wires, and sure enough, the fusible link wire is the culpret.
is there anything i can do to check it out? i do not see any splits in the wire at all. is there a way to do away with that one wire, and run my own? where does it come from and what does it go to??????????lol
thanks