Q: Battery light

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I have a Toyota Highlander 2001. After I start from a complete stop, the battery warning light comes on when the rpm is between 2500 to 3000 rpm and stays on. It goes off around 2500 rpm when the transmission is shifting down. However, when i am driving on the highway, at any speed, the light does NOT come on. Driving at nights, the headlights dim for a second and then become bright again often. I changed the battery. It was about four years old, but did not help the situation. Appreciate your advice/opinion. Joseph

My car has 240000 miles.
My car has an automatic transmission.

Hi There, It sounds like you may have a charging problem that may be a result of a faulty alternator or voltage regulator. You may have a failing voltage regulator that could be allowing the alternator to supply too much or too little amperage to the battery resulting in the battery never maintaining a consistent charge as it is designed to. The voltage regulator is a unit that regulates the charging of the battery by the alternator. I would recommend having a professional from YourMechanic come to your location to diagnose and inspect your charging system.

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