I think I already know the answer, but would like some re-assurance. '03 F150 screw Lariat w/ 5.4. Battery light came on the other night. Truck is running fine & not noticing any power dropping. If I run it real hard (over 3,000 RPM) the light goes off temporarily, but soon comes right back on. I think this is going to be an alternator starting to go out on me, just wanted to see if anyone else has had this issue & came to a different conclusion. Thanks in advance for any help.

 

Sounds about the same as when my alt went out. Battery would die slowly over a couple of days. Alt still checked out ok at advance, but new one solved the problem.

Even though the machine at advance said it was good i think we decided it was the alt when we disconnected the battery and the truck would die. I think (not positive) the truck will keep running with a good alt and the battery disconnected.

 

Thanks for the help. That was what I figured since with increased RPMs it would eliminate the problem. I knew someone here would have the answer!