xsellxoutx

well last night i was driving home to austin from houston and about half way battery light came on and my lights slightly dimmed....but i REALLY needed to get home so i kept driving and the about 30 min. later my radio turned off and my tach quit working, the whole time if i rev my car up past 4k rpm the light would turn off?......so i make it home check the alt. belt and it's ok swap the battery for another one i had in my garage and everything is good as new....well today my wife drove my car to work and she called after getting there and said the battery light came on again..........
well i guess it wasn't the battery, it wasn't the belt, so i guess i'll try the alt.....but if by reving it higher and the light goes off wouldn't that mean the alt is still good?

please help i'm confused