Chonic Alternator Failure

"I think this "blown diode" thing is being overstated. If there's enough resistance in the charge wire to cause diode problems, you are going to have smell and smoke from bad connections at the bulkhead ammeter." Actually, they go hand-in-hand; with turn-on surges and high battery charging circuit resistance, you can have the didoes go but not readily see the issues anywhere else because things are not too awful bad in a steady state mode; you see some dimmer headlights and taillights and such. Battery charging wil not look excessive since any added resistance in the charging lines will slow charging rates. Add in the marginal diodes with a cheap alternator.....I know you know the schematics by heart; just imagine some resistance in the charging circuit lines, like a poor fusible link, and where the current will come from for a sudden heavy load in the headlights. He is blowing diodes for a reason; the alternator symptoms fit it to a tee.

Regardless, he has bad regulation. The above detailed troubleshooting is pretty darned goo should be followed and the results reported. It is hard to help more without good data. Good lukc! It IS all fixable.