bouncing volt and ammeter

my car has the factory ampmeter and a under dash volt meter.when you start it it shows about 14 volts,then slowly goes up to about 15,then it starts bouncing from 12 to 16 at idle.when rpms increased to1200 or so it usually stops the bounce. Evens out to about 14.4.thought the vr was bad so replaced that and added a ground wire from one of the mounting bolts to the firewall to make sure it was grounded.did not change anything.what do you electrical goo-roos think?:poke: