When I am driving and I am on the throttle my volt meter goes down to 12 volts and when I let off the throttle, it goes back up to 14v. This is when daylight lights are on. When headlights are on, it say 14 volt all the time.

I think this behaviour could have to do with a very slow starter, when it is cold - say subzero. The battery is not very old, and with the right amount of starting amps.