Dash Reading 12.7 Battery Voltage

[MichaelRyan54]

My Dash is reading 12.7 Battery Voltage. That seams too low for me and I’m starting to suspect a weak alternator.

I recently replaced my Fuse Array because it blew, I checked the alternator at the output stud and I was reading 14V. I did a just drive and everything felt good and I was at a steady 14V on the dash during a 30 minute test drive.

on my next drive the dash was fluctuating between 12.6V and High 13’s. I understand it has a whole smart charging system so fluctuations can be normal, however I’m suspecting 12.6 is too low and I feel as I’m only running on the battery and no alternator support. Any input is appreciated before I Dive into diagnosing this and dropping some cash on a whole new alternator.

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[Terrymo]

You didn’t like the info you got from the two experienced mechanics in your other thread so you started a new one? I would listen to @alphawolff and @mwilk012 before soliciting advice from internet guessers,

 

[alphawolff]

this is normal if you had an issue you'd have a battery light illuminated

 

[Bob Burd]

I don't think he's going to be able to sleep soundly until he's replaced the alternator. Might as well get that out of the way.

 

[mwilk012]

What you’re going to want to do is press the up arrow on the left side of the steering wheel. That will solve the problem.

 

[SPPhillips]

Make sure all connections are tight on the battery and corrosion is removed.

Jeep off: measure voltage at battery with multimeter. Should read 12.5-ish volts. Indicates good battery.

Start Jeep and measure voltage at battery with multimeter. Should read 13.5-ish volts. Indicates good Alternator. Less than indicates bad alternator.

Test battery: remove all cell covers to expose electrolyte holes. Place negative lead on negative battery terminal and positive lead in each hole from left to right. If the first hole ready 12-ish volts, start from other side. First hole should read 2-ish volts and increases by 2-ish volts sequencing through the holes. If it reads the same between cells, you have a shorted cell. If cells read bad, Hook battery to a battery desulfator charger. Amazon :
YONHAN Battery Charger 10-Amp 12V and 24V Fully-Automatic Smart Car Battery Charger, Battery Maintainer
Run through battery repair setting. If it says bad battery when you first hook it up to the device, you need to hook up the battery to another battery for about 30 minutes or so to boost the voltage, remove the other battery, then hook up to bad battery desulfator again.

If Alternator is bad, you can run to have it tested at autozone, o'reilly's, etc.

I use the desulfator battery charger weekly to negate any sulfur bridging the battery plates. So far my battery is strong for 7 years now.

 

[Terrymo]

“I feel as I’m only running on the battery and no alternator support”

With a modern vehicle I think (because I’m an internet guesser) you’d be lucky to have a hour of total run time with a battery in average condition and no alternator support before the vehicle stopped running.

 

[zouch]

should we go easy on him? he's been here less than a week.

he might still learn.

You didn’t like the info you got from the two experienced mechanics in your other thread so you started a new one? I would listen to @alphawolff and @mwilk012 before soliciting advice from internet guessers,

 

[roaniecowpony]

I think the answers will be the same as your last thread. Except for some added humor to entertain us.

Your battery state of charge can be found on many web pages for AGM batteries. You Jeep is designed for AGM batteries. Don't install a common old flooded lead-acid battery. Don't charge your AGM batteries on common old chargers. Yes, they will charge it up. But in doing so, they are fucking up your AGM battery and shortening the life dramatically. BTW, 12.5v is about half charged for an AGM battery. 12.8-13v is about fully charged for an AGM, depending on brand, age, etc.
Understanding AGM Battery State of Charge: Key Insights and Guidelines | BRS Battery

If you want to find out if your alternator can charge steadily at its maximum voltage, disconnect the plug on the back of the battery monitor on the negative terminal, then plug it back in. Then drive. The voltage should go up and stay up for a few drive cycles. If the voltage goes up to 14ish for a few drive cycles, it's not the alternator.

As you probably are aware from the other thread, your voltage regulator is built into the PCM/ECM.

 

[roaniecowpony]

should we go easy on him? he's been here less than a week.

he might still learn.

 

[Terrymo]

should we go easy on him?

I’ve given this a lot of thought.
Nope, set expectations early.

 

[yokramer]

See what youre going to want to do is jack up the radiator cap, reverse the Jeep and then drive another vehicle underneath and reinstall.

 

[roaniecowpony]

See what youre going to want to do is jack up the radiator cap, reverse the Jeep and then drive another vehicle underneath and reinstall.

So, just routine maintenance then?

 

[yokramer]

So, just routine maintenance then?

Pretty much. Its either that or the problem is the loose nut behind the wheel.

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