High volts

I've read and reread this thread, to bad i'll never understand it :( Son just blew out 2 new headlights when ammeter pinned it self. It came down after a bit at idle so he idled it home. We replaced v reg, had auto parts store run system check alt ok, batt ok, starter slightly low amp draw @ 11.97 starts fine, still charging at 15.4 well it is what it is for now. I'm gonna keep reading here though.