Alternator A/C voltage question

[Bmwe5320023.0]

Originally Posted by andrewwynn

What is the frequency of the whine? If a little math (pulley size ratio and rpm) you can figure out if the frequency is 3x the rpm of the alternator or same speed that is very helpful. Also: did you test with alternator disabled via serpentine belt removed? That's the surefire way to figure out if from alternator

I'm not sure how to measure frequency in this case, but I did run the car with alternator power cable disconnected, and the whine was gone.
Which still does not condemn the alternator and doesn't preclude an electrical issue somewhere else, which just gets exacerbated by increase in voltage, caused by higher rpm