the charging system light is on and stays on. I went to auto zone and they

If the battery tests good, you may have a charging system problem. This could be a fuse, poor connection, or another charging device fault such as a alternator that is not prodcuing enough voltage (usually the cuase of the light on). It may not mean a bad alternator, but there are a few things that should be checked further. You should visit a certified mechanic, some such as our shop may do a free charging system test to better determine the cause of if there is a need to do further tests or a repair.