jfdid

Had an issue with the 06 cummins this week, drained the battery with my driving lights while parked, when I started the truck, the voltage started dropping and I got a Check Gages light. Replaced the alternator, but had the same problem. After starting the truck, the voltage would go from around 13.5 and drop continuously.
I thought it may be the voltage regulator, but wasn't.
I disconnected one battery and the truck is now charging. Must have been a shorted/wrecked battery, but all is well now.

I looked on here for an hour or two for a fix, but I didn't see this one, so I figured I'd throw it on for others.
I heard a quote once; "If you ever have an electrical/charging problem, ALWAYS assume it is the battery first."

rockcrawler304

Thanks for the info. And yes...ALWAYS, check and or replace the battery(s) first.

fitzydog

Alot of people would change the alternator. But, and a relatively big but, the alternators job is to maintain the charge of the battery, not to recharge the battery after a drain.

falstaff

uhhh, what? Since when? Our alternators are rated at 136amps- more than enough to recharge a even a dead battery. (I realize its not good for the battery) but to say the alts. are not designed for that is innaccurate I think...