battery drain

[draven]

for a few weeks now i have been having issues keeping power to the truck. i have replaced the alternator with a brand new one, had to replace the connector to the alternator cause the old on was loose, changed the battery with a brand new one and replaced the cables with brand new ones and the it just keeps losing power, ill charge it over night and itll run a day or 2 but then im stuck with a dead truck somewhere on the side of the road, i constantly everyday with a alternator and battery checker and always have the same results thats its a good battery and good alternator. also my battery gauge keeps taking a dump on me, sometimes itll read good till i go down the highway and then it jumps to L and my check gauges light keeps coming on. im at my wits end on this and i need some help.

 

[draven]

i was told to run the truck aand disconnected the battery and the truck would still run and it did but after a couple minutes it stop and shut off and looked like the belt caught
im new to workin on cars in general so i dont have the knowledge
just asking for help

 

[quacker]

I'm having the same issue on my 2013 Laramie Longhorn 6.7L Cummins diesel. I am an electrical guy, too. I was a turbine control systems tech at a power plant, so I understand something about the subject. One of the symptoms of a defective Body Control Module (BCM) can be a parasitic drain on the batteries, unusual idiot lights flashing on the instrument panel, door looks malfunctioning, electric windows malfunctioning, and accessories (such as courtesy lights) simply not working.