Ok, something is definitely wrong. Help!

[starrskream]

This is going to be long. I’m sorry.

So let’s start off with what happened the other day.

I started my truck and the battery red 12.8 V I understand that that is normal however high speeds with the RPMs above it never charged above that and prior to the battery typically 13.4 V or higher.
I drove it on the highway at 70 miles an hour at or above 2000 RPMs and the battery voltage never went up.
There was no draw on the system as I had. The headlights turned off. The climate control was turned off no electronic devices were charging and I even turned the screen off just to see if the battery would start charging above 12.8 V.

The following day, my screen had almost almost half of it turned white, gradually became black and then was all black. It did respond to touch input and then about two hours later, it returned to normal.

No, this morning I pushed the button the truck did not start. I pushed the button again. The truck started coughed and stalled in less than 10 seconds. I push the button again to start the truck and it did the exact same thing.
Then I push the button one more time it started and ran as if nothing happened.

when it finally started the battery red 14.4 V and I drove to work. At this point, I am not entirely sure it’s going to start when I leave work.

I have read online that there’s a wireless transponder is not reading the key fob correctly and my start/ stop battery and or main battery is done.

I do find it hard to believe that either battery would be dead by now, but it is a possibility as it’s likely that my truck sat on a dealer lot for several months without being started.

do you guys have any suggestions other than pulling the transponder for the short time mentioned in the picture above? I’m going to take my battery in and have it tested, but I have a feeling it’s likely toast.
Jeep gremlins be dammmed. I’m ready to hang a biker bell on my jeep lol.

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[chr15m]

Generally speaking, a charged battery is >12.6v. With the alternator 13.5-14.5, although I've seen up to 14.7v. Your battery is fine, 12.8v is great. The screen issue is unrelated and its own issue.

I'd bring it up with the dealer and if it doesnt self resolve, request a replacement.

 

[starrskream]

Generally speaking, a charged battery is >12.6v. With the alternator 13.5-14.5, although I've seen up to 14.7v. Your battery is fine, 12.8v is great. The screen issue is unrelated and its own issue.

I'd bring it up with the dealer and if it doesnt self resolve, request a replacement.

Normally I’d agree. You’re right 12.6 is normal. The concern lies in that it’s NOT going above that 12.8 when driving. It has been 13.4-14 normally when driving. Staying at 12.8 is a new thing for me.

any thoughts on the no start?

 

[JTGuy]

This might not be the best idea but I would disco the batteries and Ground out the + side for a full reboot of the system. Then reconnect it all and see what happens. Scan for codes. Might want do it at the dealer parking lot,,, LOL.

 

[ShadowsPapa]

Generally speaking, a charged battery is >12.6v. With the alternator 13.5-14.5, although I've seen up to 14.7v. Your battery is fine, 12.8v is great. The screen issue is unrelated and its own issue.

I'd bring it up with the dealer and if it doesnt self resolve, request a replacement.

AGM is 12.8 or so.
These can read anywhere from 12.5 to 15.0.
They'll read low when the battery is hot and fully charged - the IBS reports a high temperature and/or a full SoC.
In the winter if the batteries are not fully charged, it may see as high as 15.0 volts because it takes a whole lot more effort to charge a cold battery.
It will vary when going up hills, down hills, braking, accelerating and so on under normal conditions IF both batteries are fully charged.

The voltage on the dash is not battery voltage, it's system voltage - charging system as it runs. The voltage at the battery terminals would be whatever the cluster gauge says.
It's not normal to never go above 12.8 when running.

This might not be the best idea but I would disco the batteries and Ground out the + side for a full reboot of the system. Then reconnect it all and see what happens. Scan for codes. Might want do it at the dealer parking lot,,, LOL.

That'll blow the high current fuse if it doesn't take the two ground cables apart.

Normally I’d agree. You’re right 12.6 is normal. The concern lies in that it’s NOT going above that 12.8 when driving. It has been 13.4-14 normally when driving. Staying at 12.8 is a new thing for me.

any thoughts on the no start?

Do you have a volt meter? If so, open the hood, truck off and check battery voltage.
then start it and check again - get a reading at the crank battery terminals.

You can try charging each battery independently, fully disconnecting all leads from the IBS and letting it sit to the side while charging the batteries, then put it all back together and see what happens.

 

[starrskream]

AGM is 12.8 or so.
These can read anywhere from 12.5 to 15.0.
They'll read low when the battery is hot and fully charged - the IBS reports a high temperature and/or a full SoC.
In the winter if the batteries are not fully charged, it may see as high as 15.0 volts because it takes a whole lot more effort to charge a cold battery.
It will vary when going up hills, down hills, braking, accelerating and so on under normal conditions IF both batteries are fully charged.

The voltage on the dash is not battery voltage, it's system voltage - charging system as it runs. The voltage at the battery terminals would be whatever the cluster gauge says.
It's not normal to never go above 12.8 when running.


That'll blow the high current fuse if it doesn't take the two ground cables apart.


Do you have a volt meter? If so, open the hood, truck off and check battery voltage.
then start it and check again - get a reading at the crank battery terminals.

You can try charging each battery independently, fully disconnecting all leads from the IBS and letting it sit to the side while charging the batteries, then put it all back together and see what happens.

That’s the plan, haven’t had much time yet

 

[Dakarra]

I had the same exact issue at about 2 years of use and 17,000 miles. It was "sort of" intermittent until it threw a message that the auto stop-start was bad and needed attention. Took it to the dealer and they changed out the auxiliary battery under warranty. I recognize that the dealer makes mistakes too, however the problem has not returned in about 1,800 miles and about 2 months use.

 

[MudderNuker]

Back in the day, I would disconnect the positive lead to the battery and if the car died then the alternator was bad. The car would run until the battery was drained since the alternator would not charge. I am not familiar with the auxiliary battery on the JTs.

 

[ShadowsPapa]

Back in the day, I would disconnect the positive lead to the battery and if the car died then the alternator was bad. The car would run until the battery was drained since the alternator would not charge. I am not familiar with the auxiliary battery on the JTs.

And that was a horrible shadetree hack that blew a whole lot of alternators and solid state regulators.
That was started in the days of the generator. Then along came the alternator and foolish people kept on doing it even though all of the car makers clearly and plainly stated DO NOT DO THAT!
I have pictures of diodes blown in an alternator when someone did what their great uncle bubba did.

NEVER NEVER EVER disconnect a battery cable on a running engine equipped with an alternator.
I've been in the auto electric side of things since the early 70s - and I've seen my share of things happen.

The alternator needs that battery as a buffer otherwise it may try to get the voltage up ad wind up self-destructing.
Doesn't always happen, but when all of the automakers in a chorus scream that out..........

We've talked about this in several threads here over the years, I've talked with people about it on multiple FB automotive pages, and our own AMC forums - where people have ended up sending me their alternators for repair after having tried that "trick" grandpappy said to do, not realizing grandpappy never heard of an alternator before.

Besides - how would you know if it was the alternator or the regulator? Or something else causing it not to charge like a burned out dash light not allowing the excitation of the alternator?

In short - can't say this enough - DO NOT DO IT.

 

[MudderNuker]

And that was a horrible shadetree hack that blew a whole lot of alternators and solid state regulators.
That was started in the days of the generator. Then along came the alternator and foolish people kept on doing it even though all of the car makers clearly and plainly stated DO NOT DO THAT!
I have pictures of diodes blown in an alternator when someone did what their great uncle bubba did it.

NEVER NEVER EVER disconnect a battery cable on a running engine equipped with an alternator.
I've been in the auto electric side of things since the early 70s - and I've seen my share of things happen.

The alternator needs that battery as a buffer otherwise it may try to get the voltage up ad wind up self-destructing.
Doesn't always happen, but when all of the automakers in a chorus scream that out..........

We've talked about this in several threads here over the years, I've talked with people about it on multiple FB automotive pages, and our own AMC forums - where people have ended up sending me their alternators for repair after having tried that "trick" grandpappy said to do, not realizing grandpappy never heard of an alternator before.

Besides - how would you know if it was the alternator or the regulator? Or something else causing it not to charge like a burned out dash light not allowing the excitation of the alternator?

In short - can't say this enough - DO NOT DO IT.

I guess I am that old when things were simpler in cars and this worked.

 

[ShadowsPapa]

I guess I am that old when things were simpler in cars and this worked.

Some got by, but it was never a "it worked" without severe risks to the charging system if it was an alternator.

Since alternators came out in 1960 on Valiant by Chrysler corp, and then in 1963 on AMC - (BTW - AMC systems were 100% all solid state), people started learning the consequences.

Here's why some got by fine even into the 1960s and later -
GM and Ford didn't go alternators until years later - so for them, it was still ok for a few years.

 

[starrskream]

And that was a horrible shadetree hack that blew a whole lot of alternators and solid state regulators.
That was started in the days of the generator. Then along came the alternator and foolish people kept on doing it even though all of the car makers clearly and plainly stated DO NOT DO THAT!
I have pictures of diodes blown in an alternator when someone did what their great uncle bubba did.

NEVER NEVER EVER disconnect a battery cable on a running engine equipped with an alternator.
I've been in the auto electric side of things since the early 70s - and I've seen my share of things happen.

The alternator needs that battery as a buffer otherwise it may try to get the voltage up ad wind up self-destructing.
Doesn't always happen, but when all of the automakers in a chorus scream that out..........

We've talked about this in several threads here over the years, I've talked with people about it on multiple FB automotive pages, and our own AMC forums - where people have ended up sending me their alternators for repair after having tried that "trick" grandpappy said to do, not realizing grandpappy never heard of an alternator before.

Besides - how would you know if it was the alternator or the regulator? Or something else causing it not to charge like a burned out dash light not allowing the excitation of the alternator?

In short - can't say this enough - DO NOT DO IT.

yeah, that would be …bad.
Though I’ll never forget my dad starting his 81 f100 with a screwdriver lmao. Just jumped the terminals on the solenoid on the fender. “It’s fine.”

UPDATE:
Went to the dealer. No codes, screen has returned to normal. They deep tested the battery all good. (Did not test the start stop battery) radio they found a software update. Dropping it off tomorrow so they can do that. I’ll have them check start stop battery.
The no start has not returned.
I’m sure they’re going to blame my recent dash cam install, fuse taps/ add a circuit don’t cause problems like that. I tapped cig lighter fuse…

 

[ShadowsPapa]

Though I’ll never forget my dad starting his 81 f100 with a screwdriver lmao. Just jumped the terminals on the solenoid on the fender. “It’s fine.”

At least all that was doing was bypassing a switch, or perhaps a bad solenoid. There's a lot of tool boxes out there with scarred screwdrivers!
Jump the hot side to the S terminal in case the ignition switch was bad.
If it wasn't that - a pair of pliers opened up with the handles jumping battery side to starter side, bypassing the solenoid completely. Now THAT threw some sparks!

Damage? To your tools, or hands if it got hot, or possible fire if you did it next to a leaky gas line or carburetor.

 

[Wolf Island Diver]

A smart alternator doesn’t simply run when the vehicle is on, so it’s normal to not get higher voltage just because the engine is running. They’re designed to run during low load to save fuel.

Here’s a video of a guy with a Wrangler demonstrating the alternator turning off under acceleration. It’s not in English but it gets the point across.

 

[Blade1668]

A smart alternator doesn’t simply run when the vehicle is on, so it’s normal to not get higher voltage just because the engine is running. They’re designed to run during low load to save fuel.

Here’s a video of a guy with a Wrangler demonstrating the alternator turning off under acceleration. It’s not in English but it gets the point across.

I think you mean to say it's not in American English.

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