battery light came on but battery, alternator and starter are good

First check to make sure that when the car is running, the alternator is putting out ~14 VDC. If this is the case, you could have blown your mega fuse located usually where the pos. cable off the battery connects to the main fuse block. This "FUSE" is mounted on the outside of the fuse box. Just see if there is continuity between the 2 terminals at the top. Cost is just a couple of bucks at Autozone. People usually blow this fuse when changing a radio. Hope this helps. Please like if this solved your battery light problem.