Ford F150 - battery draining even while driving

Something is draining the battery on my 99 expedition. The battery was replaced last month. The car starts fine. I was driving today with the windows down and the radio on. The radio died and I couldn't move the windows. The battery indicator dropped all the way down and I just made it home. Put a charger on the battery and it charged back up. This is not the first time this happened. Took it to the dealer and they couldn't find a problem. The car will run fine for a few days, then this happens. Help please!

Did the dealer check the alternator? Sounds like a problem somewhere in the charging system, the alternator is the first place I'd look. Some places like Auto Zone will test out your complete charging system for free. Might be a good place to start.

If you have any more details or updates - please post so we can try to help.

Pull the negative on the battery with the truck running. If the alternator is good then the truck should still run, if it's bad then it should stop running.

I took my truck to Auto Zone but they were not helpful. So I tried pulling the negative on the battery with the truck running and the problem does appear to be the alternator. (I don't know why the dealer didn't suggest the alternator.) The alternator has been replaced and I have my fingers crossed that the problem is resolved. I'll post in a couple of weeks as to whether or not the problem reoccured. Thank you for your help!!!

That's a great tip, I didn't even think of that.

Glad that you got the alternator replaced. Hope that solves the problem.

The problem has not reoccured since the alternator was replaced. Thank you so much for your help!!!