Battery almost died while at stop light, now I'm hearing a dull buzzing sound

[OpenYota]

My battery has been dying for a little while but when I was at the stop light the other day my battery light came on and the radio turned off but the 4runner didn't shut down.

I turned off the lights, radio, and AC and went straight to the store and bought a new battery.
Only now I have a dull humming/buzzing sound coming from the engine bay.
I can hear it when it's in park and it slightly gets louder when I accelerate/reverse and can hear it adjust in volume when the AC compressor kicks on.
Is it the alternator that needs replacing now?

 

[jgue467]

Who knows - why not have it tested?

Any autozone or like place will test the battery and charging system for FREE.

 

[19963.4lsr5]

I had a diode block go bad and the more of a load the Alt had the higher and louder the whine got.

What’s your voltage running at.

My scangauge shows system voltage but you can buy a volt meter that plugs into the cig lighter. I have two types. One is just a voltmeter and the other is a usb charger that shows voltage when not in use or charging current.


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[OpenYota]

Update: The alternator tested good and is running around 14.2 volts.

Still am unable to identify what the whine could be

 

[19963.4lsr5]

Update: The alternator tested good and is running around 14.2 volts.

Still am unable to identify what the whine could be

Remove a belt and start the engine and see if removing anyone makes the noise go away.


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[Bad Luck]

Update: The alternator tested good and is running around 14.2 volts.

Still am unable to identify what the whine could be

Start removing belts and starting the engine to see if the noise goes away. Or get a mechanic’s stethoscope to use.