Just general info here that may not be related to your issue. When the charging system develops a fault the evidence is often seen in the light bulbs.
Last time my voltage regulator suddenly developed a fault, the evidence I noticed was volt gauge needle started twitching. I might have noticed flickering lights also had it been night and lights on. Short circuits can occur inside alternators too. Depending on how its wired, the alternator could be where your arc is coming from.
