I read all the posts on battery lights. Bunch of them. Except my problem is that mine does it at first start up and then goes off when I bring the rpm's up. Then it will stay off. With the light on my voltage is 11.8. When it goes off it goes back up to 14.3-14.5v. Once it went off I turned everything electrical on including the stereo system that draws some good current. Voltage stayed between 14.3 and 14.5. Just thought I would post because almost everyone elses comes on at high rpm's.
Unless I'm missing something I will do as Yankee7985 suggests. "Replace the alternator"

 

Changed the alternator. Works fine now except for an idle problem now. If it aint one thing it's another.

 

You got your answer in the engines section.

 

Thanks!