There is a lot of science behind this topic. So far it's not entirely sure if it's a feature or a bug

Short but ugly method: Install a new wire, let's say 10 gauge, from alt to black stud of ameter. And drill a hole going through the bulkheat so that you install ONE WIRE without any plug on its way.

Than try and you will find out if you also have other problems in your wiring - means it will melt somewhere else

Had it too: See here if u like