So the exciter wire was a mess. There was a crack in the wire at the fire wall connector. The wire didn't appear severed, but I'm sure the cracked insulation was not helping. I think the real issue might be the ring terminal. Heavy corrosion was likely making it all but useless as a conductor. I'm still in the process of rebuilding this wire, so I won't know for sure if this was the problem (or if there are other connection/wiring issues elsewhere in the harness). If I'm lucky this will be the fix of the charging issue.