I was wondering why when my 97 f-150 5.4L wraps past 3.5 - 4 grand the battery light comes on and stays on till it shifts and gets below that rpm again. I am wanting to get this fixed before I sell it and was wondering what I'm in for. ( Just ordered an 02 silver L ) The battery was recently replaced in it and it never acts like it is low. The only thing I can figure is that maybe my terminal wires have corrosion down the insulation in them, which im sure they do but I still have good battery power to the truck. Any ideas?

 

It could be your serpentine belt slipping at high rpms due to a poor belt or a bad tensioner.

 

I just told someone else this a week or so ago in another thread, but i dont think he wanted to believe me, It's a bad alternator. Plain and simple, thats what it is. Let me know what you find......

 

well looks like im gonna hafta get a new alternator......how much is that gonna run me? Also I have had a strange problem with my lights in my instrument panel going out...now tonight i turn my lights on and the lights behind the climate control panel are all out...sheesh whats up with it now??