12.7 volts while driving

[BigLizzard]

I'm on my moab trip, and looks like everything is running fine except I'm a bit concerned about the voltage while driving. Iowa currently at 12.7v. everything is acting normally regarding my electronics. Lights don't flicker, stereo works, dash looks normal, I'm even getting some of the better gas mileage I've gotten since getting these 37s on, 19.5mpg @70-75mph. No check engine lights, voltage is still technically in spec avoiding to the gauge.

At some point it reads 14v and it read 13 v today, I don't recall exactly when. It seems like I'm losing voltage but after the few hours I drive since noticing it it stayed at a constant voltage. It only changed voltage when I let up of the gas, the voltage went to to 13.x volts until I pressed the gas again

Unfortunately I don't have my multi meter with me so I'm limited with my tools. I'm hoping someone smarter than me can tell me how worried I should be. Turning off lights and stereo didn't effect voltage at all.

My thoughts are as far as possibilities, everything is fine
Is it possible the custom tune could affect voltage, does the PCM control voltage?
Could be voltage regulator, last I remember, they were on the alternator
Don't think it's the battery, but could be I guess. The truck started after I shut it off, I'll find out in the morning if it starts
Could the ripp cool packs cause low voltage.

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[ShadowsPapa]

Normal.
There's other threads on this.
Your batteries are likely fully charged, or hot, and your engine needed to have less load on it so the alternator was cut back and the voltage just maintained.

No, voltage regulators haven't been on the alternator since the 1980s in most vehicles. For Jeep they moved to the PCM in the 1990s. (the GM/Delco 10si for example, came out about 69/70 and si stood for system integrated, where the regulator was inside the alternator. Motorola also had the regulator as part of the brush assembly on some models, and as a bolt on piece instead of fender mounted for others)

These are smart charging systems now - no need to run high voltages if the batteries are full, (or hot) and there's no large electrical demand.
Prior regulation was a set voltage of 13.8-14.2, for example, and it was set. Even with battery fully charged, that's what it maintained.

With the smart control, going up or down hills, coasting, stopping, accelerating, you can see voltage drop as low as 12.6 then go up to the low 13s again, then back down as you cruise.
It's especially noted if you've been driving it a lot - highway miles, longer trips, etc. Highway miles for a couple of hours will make this more pronounced.

 

[talljeeper]

Spot on Papa. After I plug in my Noco 2A maintainer overnight I am at 12.6-12.7.. It will remain in that range for several days. After it sits for a few days it jumps to 13.5 to 14.3..

 

[ShadowsPapa]

Spot on Papa. After I plug in my Noco 2A maintainer overnight I am at 12.6-12.7.. It will remain in that range for several days. After it sits for a few days it jumps to 13.5 to 14.3..

Pretty typical. Specifics may vary with load, speed, lighting on or off, AC and other factors but that's pretty much a summary of how they generally operate.

 

[KevinM60]

What you’re seeing is how much voltage the charging system is putting into the batteries.
If they’re fully charged it’ll be running at about 12.7. When they need some charge the system will run anywhere from 12.7 to around 14.7

 

[ShadowsPapa]

What you’re seeing is how much voltage the charging system is putting into the batteries.
If they’re fully charged it’ll be running at about 12.7. When they need some charge the system will run anywhere from 12.7 to around 14.7

It's also dependent on the weather, as well. In cooler times, say sub-50s outside, these later ones will go 15.0 volts. It's harder to charge a cold battery. In really hot weather if the battery is hot, it will cut back, charged or not.

They'll run as low as 12.6 - because as long as everything is in balance and the PCM sees the engine torque is needed for motion, it can cut back and let voltage drop a bit below 12.7


The voltage will cut back if it's a hot day and the battery temperature is too high as well, even if the SoC isn't 100%.
Whether or not the alternator is actually putting anything out depends on the electric load - if the batteries are full (or hot) and the engine torque is needed for other purposes, like propulsion, the voltage will be maintained at that 12.6-12.7 to prevent battery discharge but the alternator could still be putting out 60 amps for lighting and engine needs.
Voltage doesn't mean the alternator isn't putting out, just that the PCM has decided it is in battery maintenance mode.
But these can also shut clear down if the fan isn't needed and there's no electrical load on it, kick the gas pedal down and go into high torque mode it can shut the alternator down for a bit to generate the torque needed to get up a hill with a heavy load, for example. 0 volts to the field winding, clutch disengaged, no load on the engine from the electrical system.

My normal ranges have been from 12.6 to 15.0. This 2022 has only gone as low as 126 for a very short time, otherwise it's been 12.7 after my son took it on some long highway drives for several hours. From last fall into spring the voltages ranged from about 14.5 to 15.0.

But I wish they'd stop calling these "smart alternators". They are dumb and have no intelligence to them. The alternator is no smarter than a 1963 Motorola on a Rambler. It's the PCM with the BCM and IBS that are the smarts of the system. The alternator is a puppet.

 

[BigLizzard]

Thanks for the replies. Today everything ran well. Yesterday it was hot 90+ on top of driving about 15 hours.

After 15 hours on the road I was lazy and exhausted so I didn't search the problem. I kinda planned on Shadow popping in with the insight I needed by the morning...... You fell right into my plan mwuahahaha

I appreciate the insight though. It was exactly what I needed to wake up to.

 

[Max-t]

People wonder why we went to “dummy gauges” in cars. When ya see the numbers ya start to worry. When 80% of the gauge is “normal”. With a little red high and low, it’s always fine.
I’m prone to wonder why numbers are changing… but I try to trust my warning lights to tell me if the numbers are out of range.

 

[Ironman 67]

Mine was doing this and it gradually got worse where it started going into limp mode alot.
It's at the dealership now and they have not figured out what's going on yet.

I would expect it to gradually get worse then when it gets lower it will go in limp mode

 

[ShadowsPapa]

If I had my way I've have all of the off road pages gauges displayed all the time in the cluster area. I watch for patterns and can tell when things are going to go south before they head that way if given enough information.
heck, if i could, I'd have a display choice of the spark plug firing patterns.
I had idiot lights and always have. I have a vacuum gauge in one of my cars, back in the 70s I had full gauges I installed in my first Javelin, voltage, oil pressure, tach, vacuum and so on.
Under the hood of my current Jav, I have a fuel pressure gauge and installed full AMX gauge cluster in the dash (that cost me a pretty penny)

But I know why the go/no go or idiot lights, and in the case of our Jeeps, that fake engine temperature indicator that is always normal until it's not and gives no real indication of anything other than it's working or it's broken.

Mine was doing this and it gradually got worse where it started going into limp mode alot.
It's at the dealership now and they have not figured out what's going on yet.

I would expect it to gradually get worse then when it gets lower it will go in limp mode

Not in the case of the OP - it's NORMAL.
These do exactly as he described and I've even posted documentation showing that it is made to do that under certain conditions in a prior post.
Yours likely had a charging system or battery issue.
But the way the original poster described it, it's normal. I've seen it on both of my Gladiators multiple times under the right conditions. All is fine.
As long as it does show higher voltages at the appropriate times, it's going to be just fine.

If it stays in the low charge state, there's a problem. Normally you will see other errors, including the battery light come on if the charging system isn't working.
If it's a battery problem, you would get clues if you monitored voltages and watched for patterns.

 

[Ironman 67]

It will get worse. As I said mine done same thing now it's in the shop and they have no clue what's going on. It's dead in the water

 

[ShadowsPapa]

It will get worse. As I said mine done same thing now it's in the shop and they have no clue what's going on. It's dead in the water

Nope, sorry, yours is different. You have another issue.
His is 100% NORMAL - look - read the documents I put up there. His is very NORMAL.
Both of mine do this - and it's not uncommon.
It's how it's designed. His reads in the 13s and 14s most of the time - so the batteries are charging/being charged.

YOUR Jeep isn't doing the same thing. Yours just kept going down.
(I have no idea what your volt meter is supposed to be doing/showing, why that pic - what are you trying to measure?)
His is working perfectly.
You have a charging issue. He does not and the proof is in his description of how it fluctuates exactly how it's supposed to.
I've dealt with this for a long time - apples and oranges. Look at the light you have on yours.
His is working perfectly.
CAREFULLY read his full post, then read what I posted directly from the FCA training materials and other resources.
Both of mine have done this for months and right now if I go out and start it, it will charge in the lower 14s.
His voltages react normally, in the 13s and 14s. His only got as low as 12.7 and that's a FULL charge. The situations are very different.
There's no reason for his to "get worse". Neither of mine did - all operating as designed.
You have a different issue that's not the same as his concern, which is no concern if you read his post word for word.
It's really too bad your dealer doesn't know what they are doing. Maybe I could share some TSBs with them or teach them some troubleshooting or scope the charging system for them. (I'm a former tech myself)

Look carefully at the voltages here - 12.6 is an economy trickle charge of a fully charged battery, or a hot battery, or when the engine torque is otherwise needed.
It can go as low as the lower 12s when under heavy acceleration and the alternator is shut off. But it recovers shortly after letting up on the gas.

If you see constant low voltage, you have a DIFFERENT issue and I'd scope out the alternator and do some intense testing of the batteries.

 

[Ironman 67]

Nope, sorry, yours is different. You have another issue.
His is 100% NORMAL - look - read the documents I put up there. His is very NORMAL.
Both of mine do this - and it's not uncommon.
It's how it's designed. His reads in the 13s and 14s most of the time - so the batteries are charging/being charged.

YOUR Jeep isn't doing the same thing. Yours just kept going down.
(I have no idea what your volt meter is supposed to be doing/showing, why that pic - what are you trying to measure?)
His is working perfectly.
You have a charging issue. He does not and the proof is in his description of how it fluctuates exactly how it's supposed to.
I've dealt with this for a long time - apples and oranges. Look at the light you have on yours.
His is working perfectly.
CAREFULLY read his full post, then read what I posted directly from the FCA training materials and other resources.
Both of mine have done this for months and right now if I go out and start it, it will charge in the lower 14s.
His voltages react normally, in the 13s and 14s. His only got as low as 12.7 and that's a FULL charge. The situations are very different.
There's no reason for his to "get worse". Neither of mine did - all operating as designed.
You have a different issue that's not the same as his concern, which is no concern if you read his post word for word.
It's really too bad your dealer doesn't know what they are doing. Maybe I could share some TSBs with them or teach them some troubleshooting or scope the charging system for them. (I'm a former tech myself)

Dealer already tested batteries and alternator which was fine and normal.
When I first got my gladiator it would do 12.7 and go to 14 just like his but overtime it gradually got worse.
When it drops to 12.3 boost from turbo dwindles.
I understand they say it's normal, I was told this too until it got worse and verified exactly what I was saying.
It will be a gradual decline and once he takes to dealership a few times it will finally show them.
It will be also a failure turbo boost as needed and shift program erratic

I showed techs with multimeter powertrain circuit at -03volts to give them area to look at.

Sometimes you have to prove to them . Computer shows one thing operating shoes different.

 

[ShadowsPapa]

Dealer already tested batteries and alternator which was fine and normal.
When I first got my gladiator it would do 12.7 and go to 14 just like his but overtime it gradually got worse.
When it drops to 12.3 boost from turbo dwindles.
I understand they say it's normal, I was told this too until it got worse and verified exactly what I was saying.
It will be a gradual decline and once he takes to dealership a few times it will finally show them.
It will be also a failure turbo boost as needed and shift program erratic

I showed techs with multimeter powertrain circuit at -03volts to give them area to look at.

Sometimes you have to prove to them . Computer shows one thing operating shoes different.

I'll lay $20 that the OP doesn't have further issues.
Yours is a one-off, and likely the voltage control was normal but there was ANOTHER unique issue going on with yours. You can't say because yours showed normal voltage control that they'll all fail. The thing is that ALL JTs and JLs do this - ALL OF THEM. Why doesn't anyone notice? Because they don't monitor voltage. If you had every forum member switch their screen to monitor voltage either in the cluster or the off road pages, and then drive for an extended period on the highway with batteries at or near 100% SoC, you'd find pretty much everyone has this same pattern of voltage control.
The only reason there aren't more reports is because no one drives around watching the voltage. And if they did, they'd have to "catch it in the act".
ALL of this do this, period, at least as long as they are driven often enough and for long enough.
I have seen at least 2 or 3 others report the exact same behavior here and I've posted the same documentation from STAR explaining how and why - and gee, they haven't come back with a catastrophic failure later.
That's because yours has something else going on unrelated to the way these normally operate. And it is normal.
I did an image search and found one of the other threads on this topic from over a year ago, and if I did more searching I'd probably find the others that I responded to over the last couple of years.

Diesels are more aggressive in the voltage control and will drop farther than a gas Jeep will. It is normal. The thing is that you have something ELSE going on as well.

What powertrain "circuit" are you supposedly showing? It's meaningless unless in context - which exact circuit and under what conditions.

The bottom line -
all Gladiators do this - IF - the vehicle is drive often enough and far and long enough to keep the batteries at or near full state of charge.
It's not noticed because only a very small percentage of JT owners bother looking at the gauges, especially voltage. Hey, it starts, it runs, why would they watch voltage? Temperatures are more of a concern.
If every owner of a JT left the voltage displayed in the cluster and drove for long enough times at high enough speeds in warm enough temperatures, they'd see this exact same thing.

So what you are saying is that ALL Gladiators WILL fail.

Odd because both of mine did this exact same thing, normal, it's factory programming - and both have no issues at all electrically.

Back to your volt meter - what circuit are you looking at?
"powertrain circuit" is extremely generic because there are many going to/from the PCM so which one??, what was the idea behind it putting a volt meter on it? Why?

Power train circuit is not the same as charging. So I don't get why you are saying there's a problem with the power train "circuit" because the charging system acts totally normal.
12.6 volts at the spot the voltage is measured at for the display isn't anything at all to do with the power train circuit, whatever that is, because those are all regulated. You can run 15 volts at the battery and the PCM and BCM circuits will all function normally because those are regulated voltages.

Also - yours is a diesel - it's handled more aggressively than a gas powered JT as far as alternator voltage regulation. The diesel will see lower voltages, as low as 12.2 as part of NORMAL operation. But that won't impact operation because the systems as far as control modules are regulated to operate a bit lower than that.

Oh, and here's just one of the other threads showing the same thing without catastrophic failure following -

https://www.jeepgladiatorforum.com/forum/threads/alternator-or-battery.58673/#post-963768

There's others.

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