Battery is brand new. 12.6 volts at rest. Turn the car on and it drops to like 11.5 with a couple of accessories on. Is there any other option other than replacing the alternator?
My car has 120000 miles.
My car has an automatic transmission.
This may suggest that the failing voltage regulator may not be working properly. The voltage regulator is a unit that regulates the charging of the battery by the alternator. When the voltage regulator is not working properly, this may result in the alternator allowing too much power to be delivered to the battery resulting in damaging wires and prematurely sometimes destroying the battery. A common sign of this is usually the acid inside the battery boiling causing the battery to swell. In other cases it may result in the alternator not supplying enough power to the battery, resulting in undercharging the battery or not charging it at all. I would recommend having an expert from YourMechanic come to your location to diagnose your vehicle’s charging system.
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