Q: Battery drains when coming to a stop

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When coming to a stop my battery gage will go down and my lights will go dem even when it is just idling then goes back to normal when I hit the gas. First you would think it was the alternator, So I changed the alternator and put in a brand new battery and didn't help the problem, and since the battery will drain while idling I changed the idling sensor and still no change. Have no clue what the problem is.
My car has an automatic transmission.

Hi There, It sounds like you may have a bad voltage regulator that is allowing the alternator not to charge the battery 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. You may also smell a bit of smoke due to things potentially getting too hot. 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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