On older Mopars with an amp gauge, ALL the system current that the car uses goes through the ammeter, except the starter. There can be a LOT of current going through there.

The problem is "right there." That is, either one or both of the wire terminals on the wire ends has gone bad, or the mounting/ studs/ bolts/ nuts on the ammeter itself are loose, and allowing the ammeter itself to get hot.

I don't remember what yours looks like, but some of the newer dashes are VERY poorly designed. Some of the later pickups had an all-plastic dash, and the studs and nuts which make the wire connections holds the whole thing together. If the stud(s) get the slightest bit loose, it/they get hot, melting the plastic, and getting even looser, and getting even hotter. "Snowball."

Take the thing apart, and clean everything, and carefully reassemble, maybe replace the wire ends.

Alternatively, bypass the ammeter altogether and use a voltmeter.