Alternator running hot

[stachcold]

A little while back I replaced my battery because it wouldn't hold a charge anymore. While I was doing that I decided to replace the battery cables while I was at it. It wasn't long after that my alternator had a melt down (the wires going to it melted). I had the alternator tested and it passed but I decided to change it anyways to go to a internally regulated alternator because my external voltage regulator was looking pretty rough. The guy at AutoZone talked me into getting a one wire alternator. I hooked it up following the proper internal regulator setup and everything ran fine, but when I happened to touch the alternator it was really hot. Everything else in the engine bay was only warm to the touch. I went back and checked that everything was hooked up right and it looks like it is. After everything cooled down I started it up again to see if it would happen again. After only a minute or so the alternator started to heat up again? Everything ran fine before I replace the whole battery system. Any idea's what the problem could be?