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

 

You need to put a load tester on the battery.

they are cheap and good to have.

 

Thanks for the advice John T. I stopped by Advanced for their quick in the parking lot test and they said the alternator was good but the battery was showing weak, although not bad enough for the warranty to kick in. Wonk. I'm guessing a load test is what they did as the box they hooked up had an analog meter on it like the load testers I just looked up.

Did some more testing myself and the batt shows 14.74 V with the engine running, and 14.49 V after you turn the headlights on high and fan on high.

So I guess now I'm looking for things like a slipping serpentine belt or batt terminals that need to be cleaned?

 

No if it's in the 14s with lights on your charging system is definitely working, however, 14.7 sounds high…. Now, you said your 02 Taurus? You do know this is a Jeep forum , right?
If that’s the case perhaps a Ford forum would be a better place to look