Testing alternator and excessive AC ripple?

I checked at the alt output too but the AC was so irratic my meter couldn't read it.

Off topic...
The voltage drop between neg and body was 10s of millivolts

Voltage drop between alt output and battery was 0.5v

Back to topic...

I'm guessing the mis is not alternator caused. Easy to test. Run engine with fan belt off, if it still missed not alt related.