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 also clean polish terminals and posts snd wipe the battery down. Use caution wiping as any liquid on the battery may be acid.
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?

 

[JPNinPA]

Correct. The red and black probes are in the correct terminals. The measurement select dial needs to be on the 200 in grey at the six o’clock position.

To measure you place one probe on one side/end of the wire and the other probe on the opposite end.

To make it easier. For the engine ground place one probe on the (-) terminal. Then the other on the engine block or head. If it is painted either look for a chiped or unpainted surface or the back of a bolt going into the block or head.

For chassis ground take the probe off the engine and find some bare metal on the body or the frame. I usually use the door lock catch on the body. It is either bare or paint is chipped off from use.

Post up the measurements.

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

 

[JPNinPA]

There is other items that can reduce charging the battery. One if you do not use the vehicle often that little drain to hold memory will eventually drain yhe battery.
Short rides and either too many aftermarket add-ons that the alternator cant keep up with or undersized alternator. Another is the battery temp monitor. This is a button like sensor under the battery. When it is hot outside the PCM reduces the charging of the battery to avoid damage. If this is bad you might see charging voltages of 13.2 instead of 14.4V.
If the regulator is bad the charging voltage goes up yo 19V.


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

 

[Jeepergeo]

I suggest you clean the battery terminals and inspect the leads at the same time (both ends). Clean the battery connector on each lead too. Both the terminals and connectors need to be cleaned diwn to shiney lead.

Reassemble the leads to the terminals and apply a corrosion preventer after tightening down the leads.

Check the Serpentine belt too, but I doubt that is the problem.

Next, charge the battery using a plug in charger.

Then check the voltage and make note of the reading. Then head over to AutoZone and have them do a battery load test. Have them run the the trst twice with maybe 5 minutes between the end of the first test and the start.

Cold temperatures make for heavy cranking loads and your battery may be showing its age.