Why do my headlights go dim then bright?
Why do my headlights go dim then bright? Corroded Ground Wire: One of the most common causes of dim headlights is a corroded ground wire. Bad Alternator: Another very common reason to see dim headlights is a failing alternator. If you notice that the lights brighten and dim as the engine revs up and down, the alternator should be checked immediately. Do headlights go dim after a while? Headlights that fade over time are impossible to avoid, as it's a part of how the components wear out, but it's essential that you do something about it. By replacing the bulbs,...