Automotive

Corolla: battery warning light on

  • Last Updated:
  • May 8th, 2021 8:46 pm
[OP]
Deal Addict
Feb 3, 2006
1222 posts
66 upvotes

Corolla: battery warning light on

I think I know what the issue is, but I want some feedback to confirm that I need new alternator.

Here's the problem, my car starts but the battery warning light is on.

I used a multimeter and a little tool that I bought at Princess Auto called a digital battery tester.

Here is what I found:

Cranking volts is 10.50 volts (normal according to my battery tester)

My battery tester also gave me this reading: 12.16 Alt. Idle Volts Low

And when I added loads such the radio lights etc it gave me this reading: 11.84 Alt Load Volts Low.

As far as I can tell, this is pointing towards a faulty alternator. With a load while the engine is running I should have a reading of 13 something volts.


Any feedback would be appreciated.

Cheers
5 replies
Deal Addict
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Aug 30, 2020
1077 posts
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YEG/YYZ
Check tightness of drive belt and all electrical connections leading in and our of alternator. If all good, then most likely alternator.
Deal Expert
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Dec 23, 2003
15538 posts
3845 upvotes
Toronto
Did you get a stand-alone charger to fully charge the battery?

Where are you located?

The voltage should be over 14 volts if the alternator is working. If you have a voltmeter, measure the power level at the alternator and NOT at the battery terminals to see if it is any higher. Hopefully, your serpentine belt is OK and not having any issues.
Last edited by hightech on May 8th, 2021 9:18 pm, edited 1 time in total.
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Deal Expert
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Feb 11, 2007
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Oakville
Probably your alternator, but good to give your battery a full charge with an intelligent charger. Not sure on your car, but on my BMW I was able to DIY replace the alternator regulator/brushes for about $30 to fix it. I had the same issue as you. Take care of it ASAP before end up stranded as your car will die while you're driving.
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Deal Expert
Jan 27, 2006
17918 posts
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Vancouver, BC
hightech wrote: The voltage should be over 14 volts if the alternator is working. If you have a voltmeter, measure the power level at the alternator and NOT at the battery terminals to see if it is any higher. Hopefully, your serpentine belt is OK and not having any issues.
Over 14V provided that the RPM is running at approx 2500 RPM (May vary slightly depending on the model of car).

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