bouncing volt and ammeter

had a check on charging system before replacing VR,showed the same thing that the volt meter shows.
I did too and my test said bad VR but after changing alt now its normal.

If you want measure your alt pulley dia and your crank pulley dia and post I'll plug it into my spreadsheet and see what you alt speed is at various rpms.

or do the math yourself

Engine rpm x crank pulley dia / alt pulley dia = alt rpm at a given engine rpm