i have an 2005 with 6.0 it is a xl model i just replaced the alt. and both batteries yesterday and this morning the batteries had drained so much that the truck would not crank. i charged the batteries and cranked the truck the voltage from the alt. was 14.28v. i let the truck run for a while and when i cut it off the voltage on the batteries was 12.58 i went back out and checked the batteries again 3hrs later and the voltage was 12.18v what would be a good thing to check for the drain?