your battery is probably boiling over because the grid heater in the intake takes so much current until the truck warms up that the alternator is sensing both batteries are dead
never run a diesel truck with one battery or a good battery and a bad battery; between the intake heater and the starter it will draw a battery down really quick and the alternator will recharge it so quickly it will boil over
if it is the regulator its in the computer bad an external one can be put on in a matter of minutes from one of our older mopars
