I have an 03 7.3 I bought about a month ago. Ran great until one day it wouldnt start, took it to shop, they put new alternator on it. Next day battery light came on, but it went off with in a few minutes, this trend contiued for a few days with th light coming on for a minute or two then going off. I tried to take it to shop but when I did light went off and they could not get it to come back on, so they could not find anything. Today it came on and stayed on for an hour while driving. Any ideas? I

 

I've had issues with new alts being bad. I like to pull the alt off and take it to auto parts store to test it. They come off so easy I've pulled them several times in the auto parts store parking lot to get it tested, just make sure to have rags cuse it'll be hot.

 

check your wiring and your connections to it. when a the light comes on its telling your truck that your alternator is not sending a charge to your battery . happened to me before if the wiring is fine go get it tested. but id check the wiring mine dry rotted and caused this problem