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

 

[TerryMason]

I'd start by checking the belt going to the alternator. Verify that is tight and in good shape.

Next, I think (but have never done it myself) that Advance Auto (and likely others) can test your battery and alternator for free.

I would expect that the battery light monitors the charging voltage, and is likely more of an indicator of alternator health than of battery.

 

[superj]

12.48 is a hair low.

Each cell should read 2.2v so you should have 13.2 but 12.48 would still start most older vehicles.

I agree with terry that checking your alternator is a better choice with the light coming on.

 

[bradleyheathhays]

Thanks for the info guys. Well, we have quite the mystery here then. I did some more testing and the batt shows 14.74 V with the engine running. With the engine running, high beams on and high fan on the batt reads 14.49 V.

Got the old girl up to Advanced for their quick parking lot test and they said the alternator looks good but the battery shows weak, but not enough that the warranty would kick in. Wonk.

So I guess what I'm looking for now is a serpentine belt not turning the alternator like you suggest Terry or maybe batt terminals that need cleaning?

Since the dash batt light is a function of the charging system I could see how a loose serpentine belt might trigger the light, but would dirty batt terminals cause it as well?

 

[JPNinPA]

12.48 is a hair low.

Each cell should read 2.2v so you should have 13.2 but 12.48 would still start most older vehicles.

I agree with terry that checking your alternator is a better choice with the light coming on.

Each cell should be 2.1. v giving 12.6V
12.4 is low.
Get the battery load tested and alternator tested as described above.

Cold weather takes out batteries.
Id a look so clean polish terminals and posts.
Inspect and ohm out your power and ground wires. Resistance should be less than an ohm.


Never look down on anyone unless you are helping them up - Jesse Jackson

 

[bradleyheathhays]

To me, ohm is something you say during a Buddhist meditation. I'm afraid we've just reached the edge of my understanding of how to operate my multimeter. I understand that an ohm is a measure of resistance, but I'm not sure where to set my meter's dial and where to put the probes to measure what. Dial, I'm guessing straight down to the gray 200 mark. I'm assuming testing for Ohms is another way of searching for something like terminal corrosion or a connection compromise somewhere along the line?