Q: Irregular power and idle

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My battery light first started popping on after the alternator was replaced in about July/august. At first there was no really symptoms other than that. The battery was checked numerous times and it checked out fine. After a few months I could start to hear the idle speed change when the battery light came on. I also started to notice the dash lights and headlights "surging" up and down while driving and idling. I've posed the question to numerous car people and can't get a definitive answer. The most common answer however is my idle air control is going bad. I just want to know for sure so I know what to do next. Thank you. Kendra.

My car has 97000 miles.
My car has an automatic transmission.

Hi Kendra, Your idle air control valve as you may know monitors air intake as it enters the engine while the computer uses this info to make adjustments to the air/fuel ratio. When this is dirty or not working properly, this may cause the idle to fluctuate as you have described. The surge in the lights going up and down may suggest that you may have a faulty alternator or voltage regulator. The alternator charges the battery as the engine turns the alternator, so it may be possible that the struggling idle may impact the charging system as well causing a drop in the system voltage which results in the lights surging. I would suggest having a professional from YourMechanic come to your location to diagnose and inspect your car.

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