Battery light intermittently turning on

Tiny
JITHIN MATHEW
  • MEMBER
  • 2004 TOYOTA HIGHLANDER
  • 3.3L
  • V6
  • 4WD
  • AUTOMATIC
  • 220,000 MILES
My battery light is intermittently coming on even after replacing my alternator and battery. They both were tested as bad and that's when I decided to replace them. I noticed that my new alternator is charging at 13.75v even with my headlights and radio on. Is that normal? The car starts up and runs fine but the battery light just keeps coming on. I tested the alternator at advance auto before I installed, and it passed on their machine.
Sunday, November 21st, 2021 AT 5:22 PM

15 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
This could be a couple things, but we need to start from the basics even if you have already done them. I would stop by a parts store and have them check the battery and alternator again. If either of those are faulty then that needs to be addressed first.

https://www.2carpros.com/articles/how-to-check-a-car-alternator

https://www.2carpros.com/articles/car-battery-load-test

If the battery and alternator are okay now, then we need to run through the testing I am attaching to make sure we are not missing something else like the belt being too loose or slipping.

Also, the voltage that it is charging is ok, but if the indicator is coming on then that means it is not reaching the level that it is being commanded.

So, let's start with this and go from there.

Thanks
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Monday, November 22nd, 2021 AT 6:58 PM
Tiny
JIS001
  • MECHANIC
  • 3,412 POSTS
Quick question. Did you install factory parts or aftermarket alternator?
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Monday, November 22nd, 2021 AT 9:53 PM
Tiny
JITHIN MATHEW
  • MEMBER
  • 71 POSTS
It’s brand-new aftermarket alternator and brand-new interstate battery. Shouldn’t the voltage go up when I run my accessories?
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Tuesday, November 23rd, 2021 AT 7:04 AM
Tiny
JIS001
  • MECHANIC
  • 3,412 POSTS
The 13.75 volts is your normal range. Double check your alternator fuse to verify it has not gone open circuit. Make sure your belt is not losoe or slipping. And as KASEKENNY1 pointed out, have the charging system checked once more.

I have seen some aftermarket alternators cause the battery light to remain on. You may need to replace it once more. Keep us posted after your checks.
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Tuesday, November 23rd, 2021 AT 8:27 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Correct. When you add more loads to the system the voltage command will go up but if the light is still coming on then that may be because the new alternator cannot meet the command.

So, if we assume the alternator is okay, we will never fix this. So JIS001 is correct that many times the replacement alternators are no good, but that assumption is made, and we lose a lot of hair trying to figure it out.
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+1
Tuesday, November 23rd, 2021 AT 9:36 AM
Tiny
JITHIN MATHEW
  • MEMBER
  • 71 POSTS
Hello everyone, I tested the alternator, and it failed the test, so Advance gave me a new one and I put that one. After a few days of driving the car pretty much was having a voltage surge and everything in the car was going crazy and my battery light was just flashing because of it. I decided to replace it with one from AutoZone and now the car is running fine, but my battery light is steady. I checked the voltage again and it was producing 13.9 volts while the engine is running. The battery is new as well and all the connections are secure on the alternator and the battery. Any fuses that I should check?
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Sunday, January 2nd, 2022 AT 11:41 AM
Tiny
JIS001
  • MECHANIC
  • 3,412 POSTS
KASEKENNY1 has provided the wiring diagrams with the fuses already. In the engine bay fuse check the alt fuse 7.5A and on driver lower part of dash is the ECU-IGN fuse 10A and heater fuse 10A. Let us know how those fuses look.
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Sunday, January 2nd, 2022 AT 12:20 PM
Tiny
JITHIN MATHEW
  • MEMBER
  • 71 POSTS
Hello, thanks for the reply. I will take a look at it and will let you know. I was wondering, if a alternator fuse is blown then there wouldn’t be any power going to the alternator wires right? In my case, the alternator has power and it’s producing good voltage.
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Sunday, January 2nd, 2022 AT 2:37 PM
Tiny
KASEKENNY
  • MECHANIC
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Take a look at this wiring diagram. There is a fuse for each wire going to the alternator.

So, we need to go to the alternator and check the power at each of the wires specifically, B, S, IG.

Your alternator fuse could be fine but if you don't have power on the other wires then the alternator will not work.
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Sunday, January 2nd, 2022 AT 6:31 PM
Tiny
JITHIN MATHEW
  • MEMBER
  • 71 POSTS
Hello again,

I checked all the fuses, and they are all good. I tested both the battery and alternator again and they passed the test and are producing good voltage. I heard that the EB2 connector is known to get corroded on these cars. I haven’t had a chance to look at it yet but was thinking of buying the plug ahead of time before I take it apart. I am having a difficult time finding the connector anywhere including the dealership. Any suggestions?
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Friday, March 4th, 2022 AT 8:32 AM
Tiny
KASEKENNY
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Got it. That is correct as I have heard of that well.

I am attaching the location of it, but I have not been able to find a kit for it.

What I would consider doing is just getting an entirely new connector which means both sides of it. All you need is a 10-pin connector and then change one wire at a time to ensure you keep them straight. However, you don't have to keep the exact replacement connector if you are going to change both sides which is what you would have to do if there is corrosion.

Here is a video that will show how to cut and solder the new connector in:

https://www.youtube.com/watch?v=PxA5wczsCVo

Please let us know what you find. Thanks
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Friday, March 4th, 2022 AT 12:50 PM
Tiny
JITHIN MATHEW
  • MEMBER
  • 71 POSTS
Hello again,

I checked the EB2 connector, and it is fine. There is no corrosion inside or none of the pins are broken inside, but my battery light remains on. Other than very little buildup of the green stuff, the pins and wires looked fine. I checked the voltage and it’s usually steady at 14.06 and but sometimes will go up to 15 when all the loads are running. My guess is that the battery light is sensing wrong voltage which causes the battery light to come on. Is there a sensor for this that could be causing the problem and if so, where would that be?
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Saturday, March 12th, 2022 AT 4:55 PM
Tiny
JIS001
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If everything is checking okay, then it sounds like you will need to replace the alternator with a dealer part. But before you go that route, can you post a picture of the green stuff you see? If it is corrosion, it can affect voltage. Sometimes it is just grease from the manufacturer to prevent fretting.
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Saturday, March 12th, 2022 AT 11:21 PM
Tiny
JITHIN MATHEW
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Hello, I will post a picture of the green stuff. I don’t know how many amps the stock alternator was so I put 100 amps twice from Advance Auto, but the part was becoming defective after couple of days. Right now, I have a 130-amp alternator from AutoZone, and it’s being tested as good. Will the higher amperage cause it overcharge? I checked it with a multimeter and the car is charging at 14.06 volts and sometimes going up to 15. Battery light is remaining steady now.
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Sunday, March 13th, 2022 AT 7:03 AM
Tiny
KASEKENNY
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No. The higher amps are not going to over charge the components.

Amps is the flow of electrons and voltage is the "pressure" needed in order to make the component run. So, you can have proper voltage but not enough amperage to turn the light off.

If the alternator is now the larger one, I am going to think you have an issue with wiring.

I would suggest using a scan tool and watch the ECM data to see what the battery voltage is.

The way this light works is the ECM tells the cluster to turn the light on via the communication network, so we need to see what the ECM is showing as the voltage readings. It could be telling the cluster to turn it on incorrectly.

If this is not the issue, then we may have an issue in the cluster because it appears the vehicle is charging properly. Has the battery drained at all?
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Monday, March 14th, 2022 AT 1:56 PM

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