Battery indicator light on

AS OF 1/2/2022
The battery light on my dashboard just came on.

I looked at the battery, and it is from AAA and the sticker shows that it was purchased in 2021. I haven't checked it with a voltmeter yet.

Also, I hear a whining noise when I'm in idle. The whining noise lessen when I step on the gas, but it's still there.

Does anybody know what the issue is?

-Tacoma 2006 V6 TRD Off-Road
180,000 miles

UPDATE AS OF 1/4/2022:
So, after I let the car sit for a day, I decided to test it again.

When I started the engine, the battery indicator light is now gone. Also, when I first started the engine, there was a brief whining noise, but that quickly went away. Usually there's a whining noise on first start up as the weather has been getting cold.

Also, as I progressed through the test, the whining noise seemed to disappear as the car warmed up.

Additionally, it has been cold lately. I'm in SoCal, and it's been under 60 degrees Fahrenheit.

Here are the results for the voltage readings after performing 3 different test :

*1st Test: Performed with Radio and Amp disconnected
Initial Voltage Reading (Engine off): 12.47v
Voltage Reading (Engine on): 14.23v
Voltage Reading (Engine on w/Accessories on): 14.14v
Voltage Reading (Engine off): 13.14v (surface charge)


*2nd Test: Performed with Radio and Amp connected
Initial Voltage Reading (Engine off): 12.54v
Voltage Reading (Engine on): 14.13v
Voltage Reading (Engine on w/Accessories on): 13.87v
Voltage Reading (Engine off): 13.07v (surface charge)


*3rd Test: Performed with Radio in screensaver mode and Amp disconnected
Initial Voltage Reading (Engine off): 12.52v
Voltage Reading (Engine on): 13.97v
Voltage Reading (Engine on w/Accessories on): 13.81v
Voltage Reading (Engine off): 13.13v (surface charge)


*** without the surface charge, it will measure around 12.54v after turning off the engine and leaving the headlight on for a bit

The serpentine belt is tight.
The alternator is spinning.
Wires are not loose.

For the voltage drop test, I tested it with the engine running and accessories on. However, I didn't have someone rev the engine. But the voltage reading from battery negative terminal to the case of the alternator is: 0.02-0.03v

 

Probably a bad alternator, they like to whine when they're on the way out. Pull the field connector (small plug) and see if the whine goes away, if it does it needs an alternator

Load test the battery too, a weak battery will stress out the new alternator as soon as you install it.

A decent backyard battery test is to disable spark or fuel, crank the engine for a good 5-6 seconds and watch to see if the battery voltage drops below 10V

 

99% of the time if battery light comes on, its an alternator, likely brushes have worn thru the slip rings, it will fail again.... that being said I worked on a 2018 ford f150 today it was the circuit breaker (same as a fusable link that blew on the heavy wire from the alternator, it triggered the battery light warning)

 

Yeah, but... he shows 14 volts with engine running, which usually means it's not the alternator.

The whining is the alternator working hard at low rpm. Did the batt. light come on while idling with the amp, etc. running?

It could simply be that the battery can't support the sound system at idle.

 

The first time (and only time) the battery light came on, I was reversing out of a parking spot. Once I put it into Drive from Reverse, I realized that the battery light came on and there was a whining noise. (Also, I had the radio volume very low at this time since I was reversing)



I drove home and I tested the battery voltage with a multimeter. I disconnected the amp and removed the radio faceplate... On that day, with the engine running and with no accessories, the voltage reading was 13.4v. After I revved the engine a couple of times, the voltage reading was 13.7v. (This was with the battery indicator light on)

Also, the whining noise was loud and unmistakable when the battery indicator light was on.

 

Interesting... Since the battery indicator light doesn't show anymore, the whining noise seems to be gone as well. So, I couldn't test the field connector.

But when the alternator was whining, it was an unmistakable sound.

 

It is possible for the whining to go away and eventually come back?
When I drive with the AC on and slow down to a stop, a couple of seconds after I stop I feel a small thump. Kind of strange, because without the AC when I come to a stop, that same thump is not there anymore. I kind of wonder if this is the Alternator causing this thump as well. This only happened for the last 2 months btw.

I'm thinking it may be best for me to just go ahead and change the alternator along with a new serpentine belt.

 

That thump is likely the AC compressor kicking on and off.
It’s normal.

 

When my alternator failed it was intermittent. Battery light on, not charging, then OK with normal charging voltage the next time. Until it came on for good.

 

Tacoma 2006 V6 TRD Off-Road....180,000 miles
If thats the original Alternator its been a good one...

 

It's the alternator. Just take it in to any auto parts store & they'll check it to be sure.
Battery light coming on is indicative of a failing alternator.

 

Ohh, that's good to know! I was wondering about that thump for a while. Thanks

 

I think that's how mine is reacting now or is going to react... I guess I'll plan to changing it this week.

 

Yup, it's the original alternator!

How long do they usually last?

 

Can they check the alternator while it is still on the car? Also, what's the chances that they'll find something wrong now that the battery light is gone?

 

If the battery light is off it's likely charging.

Put your voltmeter across the battery terminals, turn the truck on, turn on a bunch of electrical accessories like fan blower, high beams, etc and see if it puts out close to 14 volts

But it would be nice to do this when the warning light is on

 

They can test it still mounted. But since you already know it's sometimes not working, best to go ahead and replace. Do yourself a big favor and do not replace with something from autozone. Stay with oem denso, or denso reman.

 

bout 17 years

 

I just called the Toyota dealership. They gave me this part number: 270600P02084

I believe it's remanufactured. I forgot to confirm the brand when I called them. Also, it doesn't say on the website either.

Hopefully, it's Denso.

Also, should I buy the serpentine belt from the Dealer too?

 

I see what you did there hahahahaha