Old alternator was replace for not charging battery. This is the second alternator I replace because the first one was bad as you said , the weird part which don’t make send to me is that if I disconnect the alternator plug a few times and plug it back in squeaking goes away alternator charges...
I replace alternator and battery , voltage at 12.85 when off and 14.45 when running but as soon I turn lights on rpms drops alternator belt squeak and alternator stops charging if I disconnect alternator plug rpms go up like is has no load and voltage goes up again .. I rewire it and same thing...