Occasionally, notably when the battery is in a minorly discharged state (but
not always), I'll get an alternator offline indicator light and see the
ammeter go negative. This will either disappear immediately on its own or
require an alternator switch off/on reset by the book. It's been
intermittent for a year and the mechanics can't isolate it. Any ideas
appreciated.

Peter Shurman
Bonanza F33-A C/GRDT