Get your battery load tested, it's free at any auto store. if its going bad and cant hold load it will starve your amps.
honestly it sounds like there's something else wrong, even when you drop from 14v to 12v the difference is barely audible - to me at least. it'd have to be a serious starvation of power to lose that much output
honestly it sounds like there's something else wrong, even when you drop from 14v to 12v the difference is barely audible - to me at least. it'd have to be a serious starvation of power to lose that much output