Batt showing 12.48V

[bradleyheathhays]

I have an 02 Taurus and my dash battery light has come on twice in the past week.  Once after a few miles of driving, seemingly random, and once when I was warming the engine up.  It's been 20-30F around here lately.  This second time, I started the engine in the morning at about 20 deg F.  Let the idle come down to normal and after about a minute I gave a little gas to get the engine up to 1500 rpm, which is when the batt light came on.  It switched back off after about 5 seconds, after I got off the gas.

 

After sitting for 6 hours, my old multimeter shows 12.48 V on the battery.  It's one of those 2 year warranty EverStart batts from Walmart, manufactured in 3/23, so still in warranty.  

 

Does a 12.49 resting voltage justify a warranty claim, assuming it's not the alternator that's going bad?

 

Thanks

[akirby]

The light indicates a charging problem which is usually the alternator not the battery.  It should be around 14.5V when running.  Might want to replace the serpentine belt if it’s old.

[bradleyheathhays]

Aha, serpentine belt was not in my thoughts so I'm glad you mentioned.  Do you think these 20 deg F temps might be causing it to slip some not spinning the alternator as fast as it should?

 

Got some more testing done.  With engine running the batt shows 14.73 V.  With the engine running and high beams and high fan on shows 14.49 V.  Took it to Advanced for their test and they said the alternator looks good but the battery shows weak, but not so bad the warranty would kick in.  Wonk.