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Q: Battery light illuminates at 70 mph and turns off once vehicle speed dips below 60 mph.

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My battery light keeps going on after 70 mph and will go off once I go slower than 60 mph. Alternator problem?

My car has 92000 miles.
My car has an automatic transmission.

Make a note of what rpm the engine is doing when you are at that speed causing the light to come on. With the car stopped in park, see if you can rev the engine up to that speed and cause the light to come on. If it does, a mechanic can check the charging system for the problem. It is possible that the alternator brushes inside the alternator lost contact at higher speeds and stop charging. A professional fro YourMechanic can come to your location and test the charging system and replace the alternator if it stops charging or overcharges.

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