why does my battery light come on and off? on 1991 Mercury Capri

have changed the belt and battery and still has the same problem, sometimes the light is dim.

Asked by for the 1991 Mercury Capri
Hello Dad! Your battery light is coming on because there is an issue with the charging circuit...either your alternator or battery is failing (or both)...have it checked right away so you don't get stranded Dad...