Black wire with Orange stripe, and Yellow wire with white stripe are your main FEEDS to the fuse block.
Iffin you're melting those suckers, you got a problem elsewhere! Fixing the wires will be fixing the results, not the problem. Find/fix the problem, or else put the local Fire Department on speed dial!
This is NOT something to play with. Get the alternator checked first, then start on the fusible links. Check for shorted wires on exhaust/headers etc etc. Don't play with this one bro, we'll lose a Pony if you do!
It's prolly gonna be something simple, but I wouldn't be willing to take the chance. I had one on fire once, and it wasn't pretty. Find out what it is, and FIX it! This is a serious problem, although probably an easy fix. The melted wires are a symptom of the problem, FIND THE PROBLEM, then fix IT, then fix the symptoms.
Wit me?
