The battery light on my 2000 F-150 flickers on and off when I get to 4000 RPM and stays on after 4500 RPM. The only time the RPM gets this high is when I pull my trailer up a steep hill. My Amp gage stays in the middle range and does not show overcharging. The truck starts quickly and everything operates correctly. Any Ideas, other then keep the RPM below 4000 and don't pull my trailer up steep hills.
Thanks,
Pat

 

Pretty much an alternator problem. Below the fault point the system works as it should so you won't tend to see any other effects from it.
I pull about like you and have no charge fault like that.
Might be possible that an Auto Zone could test the alternator for that fault if they spin it fast enough.

 

I had the same problem with my 97, just replaced the alternator.

 

Replace the alternator. The alternator brushes are worn and bounce at higher engine rpm, therefore the battery light illuminates. The brushes will continue to wear and the battery light will come on at lower engine rpm until finally on all the time.

 

I installed a new alternator and belt. I was surprised that it only took me 1 hour. The toughest part was the belt. Everything is operating correctly. The light doesn't come on at any RPM. Thanks so much for all of the help. Now I can take my 2500 mile vacation from California to Buffalo Wyoming and back.

 

Hope I am doing this right ....first time back on in a couple of months and everything has changed... I noticed my battery light come on last night when I was passing someone....I have 40,000 miles on my 2002 screw and alt shouldnt be worn out....also my fan speed on a/c slows down under this condition, just wondering if this also happens to you guys

 

Can't hide behind the thought that the alternator should not be worn out.
It's not, just has a fault.
Change it like suggested and have it over with. Your beginning to have other affects from it now.
Like to get stuck along the road with a dead battery and no trailer lights?
My DPFE failed with 53000 miles. Had to change it or look at a CEL light that won't tell me when other faults occurr because it's already on, unless code readout is looked at.
You gotta do what you gota do!

 

My alternator lasted 32000 miles before the light started to come on. Must have been built on a Friday or Monday. I just pulled our 5th wheel from California to Buffalo Wyoming and back without any alternator problems. I am sure glad I changed it before our trip. Thanks again for everyone's response.

 

A man on the move.
Good to hear of a nice trip.