Need Help with batt/alt problem!

[diablo350]

Hi, last week, my truck would not start. I put it on a charger for a while so I would at least get to work. I tested the batts, and it said that they just needed a recharge. I decided to just change them out. Everything was great until this morning. I went to start it, and the batts were dead. There is not batt light on, and I do not have any aftermarket parts plugged in and there are no lights that stay on during the night. Does anyone have any idea about this? BTW, it is a 2003 F350 6.0. Any help is greatly appreciated. Thank you.

[bigcountrysg]

Check the connections and clean them. Clean the alternator connections as well. Test the alternator for output. Should be putting out around 14 volts. Inspect the belt as well. Replace parts as needed.

[Bamfster]

The ALT needs to be putting out a minimum of 14.75 volts to keep the truck running as well as recharge the BATT. Anything less and the BATT(s) won't stay charged.

[diablo350]

I tested the Alt. It is putting out only around 11v. I called around to find the best deal on a new one, but no one could tell me what the amp were. I finally got one from the dealer, cause I know it will be the right one. The only thing that I don't like, is the 12m 12000 mile warr. I really don't think I will have the truck by this time next year anyway. I just wanted the right part so I don't blow anything up when I tow. I am thinking of downgrading to a smaller truck cause my bro had a Dodge 2500, so if I need anything big towed, I'll just get his truck.