if the wire is the stock wire, heat means resistance that shouldnt be there, ie a bad connection somewhere. that lil 8 or 10 gauge wire is kinda marginal for the length, imho. if you can, replace it with 4 or 2 gauge wire and connect the stock alt wire to the positive batt terminal, as its what supplies juice to the factory fuse box. or if ya wanna do it on the cheap, just check and clean with a wire brush or file all the connections. also check all the wires for fraying, damage or corrosion

good luck!

'94 X-Cab, EB inside and a few fabbed parts. My wife: "How about you stay on the road?" Me: "I drive a Toyota truck, the road is OPTIONAL!"