Color me confused.

While I completely understand how an alternator swap can eliminate whining due to aging bearings, I do not even remotely understand how an electrical terminal can cause such noise.

 

Yeah, no idea either but I went to a specific starter and alternator shop who only specialize in starters and alternators for 40 years. They immediately pointed out what the whining noise was. As soon as I replaced the alternator, the noise was gone and the battery was recharging as normal. It's been 2 weeks since and haven't had any issues.

 

I'm betting it was the alternator bearings.

 

That's the main power terminal.

Outside chance(?) of the insulation surrounding that having some cracks or defects. "Leaking" would be like a partial breakdown of the insulation causing some power to short across. Then the alternator would be working much harder than normal.

The diode bridge is inside that sheet-metal enclosure with the 3 nuts. I wouldn't be too surprised if losing one of the diodes or shorting (leaking) across one is what they were really talking about.

 

I feel something was lost in communication between you and the mechanic. or your pulling my leg... both are reasonablel...