I have a similar issue previoulsy posted about a weird battery light. In my case, I noticed my battery light would flicker, stay illuminated for differing amounts of time, and then go off. The headlights would dim as after I stopped. Yesterday, it stayed on, had a local parts store test things out, and I wound up replacing the battery. The light remained off for the rest of the day. Today, however, it stayed illuminated all the way into work (about 35 miles), but did it's little flicker trick when I stopped at traffic lights. I'll go check for loose wires, etc., but am I looking at replacing my alternator?

2000 F-150 XLT
152000 miles

 

Start out with putting a set of wires ( fused ) from the battery, up the fender into the cab. Hook up a meter to the leads, and check the voltage when driving, to find out if you are over or under charging. This would be a good place to start with, rather then just replacing stuff without testing.

You made no mention of it, are the battery terminals clean and tight ? I would suspect so, with just replacing the battery. Did you check the other end for corrosion and tightness ? I am drawing a blank, but is there a fuse on the '00 just behind the battery on the firewall for the alternator circuit ? My '01 has only been gone for about a month, and the layout is quickly disapearing from my memory... If it is where I think it is, is the fuse fully seated, and the contacts clean ?

The reason for the clean/tight questions, is it could be adding resistance to the circuit, and the battery might not be getting the full charge output from the alternator, and maybe causing the batt light ?? Just guessing, until we get a bit more info.

 

If you check the items SSCULLY indicated and it still acts up, be prepared to buy a new alternator.