91 Gt 1.8 of course

Someone put an alt on the car and when the battery was connected it blew the mega fuse under the hood. I figured that it is about a 12/14 ga wire that is the problem. He had it connected to the back of the alt where a ground should go but it is hot. Anyone have a clue what and where this may go to and where I can find a ground for the alt. The plugin is connected but it still is not putting out power.