Saw 15.3 volts today

[WILDHOBO]

I will try that, spending some time under high voltage lines. It may help my brain think faster and clearer. Then I will be able to solve the great mystery of life and conclusively determine which oil is truly the best for the 3.6.

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[tysongladiator]

Funny thing - when this first happened, I had two thoughts:
people pulling cables off to "test the alternator" and spiking voltage, blowing things apart, and loose connections causing voltage regulators to sense incorrectly.
A bad ground on an AMC can cause voltage spikes - especially if it's the regulator ground as it will see a lower voltage due to the voltage drop across the connection and try to compensate.
and
your video.

I knew the likely cause, but your video suggests that the battery terminals are a common point of contention with these. So, I likely won't have to spend much time looking for that bad connection, can go right to it.

And here's the crazy thing, I have an aftermarket battery and aftermarket terminals and I still have to keep a shim in between the terminal and the post to keep it tight. Crazy!

And I just went through the same thing with my tractor. I have never even touched the battery. But a few weeks ago, it wouldn't crank. Not even turn over. Pop the hood and the terminal wasn't tight.

Or maybe it's just me. But I now check all electrical connections frequently for good, secure connections. It has definitely created a slight case of paranoia within me.

 

[Chaos Theory]

This is more likely than people are giving you credit for. I've read reports of electrical readings being way off minutes prior to a nearby lightning strike, microwaves can block wifi signals, and solar flares can make electronics act up.

My favorite electrical trick is making a fluorescent bulb turn on without being connected to anything by holding them vertically beneath high voltage power transmission lines.

Yeah, it was an entirely serious comment. The largest geomagnetic storm in 20 years hit on Monday and could have been some residual. *shrugs*

 

[Master_Cylinder]

I love how the Mrs immediately blamed you! You’re sitting in a Jeep lady, you should know better!

 

[Bandit’s Lair]

I love how the Mrs immediately blamed you! You’re sitting in a Jeep lady, you should know better!

You could say that but I’d recommend pads and helmet beforehand. Maybe full body bubble wrap. Oh!! And an upgrade on the health insurance!!

 

[ShadowsPapa]

Yeah, it was an entirely serious comment. The largest geomagnetic storm in 20 years hit on Monday and could have been some residual. *shrugs*

It's done the radio volume thing before. If you have the steering wheel turned at all and the volume is at, say, 3 and you try to up it to 7 or 8 with 5 or 6 clicks of the steering wheel button - it will climb fast to full blast and there's nothing at all you can do even with the round volume knob until a few seconds have passed. It's a "this happens once in a while" thing and I should know better than to try to adjust radio volume with the wheel turned and/or just after starting it.

The voltage thing appeared more to be connected to other factors I'm still investigating. The radio was in no way related - it's happened before. The voltage was seriously more like a bad connection situation. Ironically, even my charger acted like the batteries were really low when I got home and connected it, and yet the ESS worked perfectly that day.

 

[Wheelin98TJ]

Are Gladiators below average for reliability of electronics? It seems like they may be.

 

[Radio Guy]

How old is the battery and its it stock or replacement? I've run across old batteries in solar systems where the electrolyte was very low and would not take much of a charge and the charger voltage ended up very high like you are seeing. Along with the other suggestions I would do a battery test to see if its toast.

 

[WILDHOBO]

Are Gladiators below average for reliability of electronics? It seems like they may be.

Only on forums.

 

[Wheelin98TJ]

Only on forums.

And in my driveway.

 

[ShadowsPapa]

How old is the battery and its it stock or replacement? I've run across old batteries in solar systems where the electrolyte was very low and would not take much of a charge and the charger voltage ended up very high like you are seeing. Along with the other suggestions I would do a battery test to see if its toast.

Whole truck is April 2025.

 

[BambiBasher]

I’d be curious myself what you find because mine is constantly at 14.8-15 even when it comes off the battery tender.

 

[yukonosufan]

Could be an alternator with a bad voltage regulator. Just helped a friend change an alternator on another vehicle because the alternator was putting too high a voltage to the battery. This will also affect the electronics in the vehicle to act funny. If I remember right, my friends car was reading 15.8 volts with it running and battery voltage not running was around 12.7 volts. Radio and fan controls would work not running and would not work with the car running. Something else to consider.

 

[ShadowsPapa]

Could be an alternator with a bad voltage regulator. Just helped a friend change an alternator on another vehicle because the alternator was putting too high a voltage to the battery. This will also affect the electronics in the vehicle to act funny. If I remember right, my friends car was reading 15.8 volts with it running and battery voltage not running was around 12.7 volts. Radio and fan controls would work not running and would not work with the car running. Something else to consider.

These don't have internal voltage regulators.
It's all done by the BCM and PCM working together - a "smart alternator". It's actually settled down and is working as normal for 0 degree weather - sticking in the 14.8 range most of the time.

You likely changed out a Ford or GM system - perhaps one of their older models with internal regulation. They don't have that - and haven't for decades. Jeep went to PCM voltage control back in the 90s.

The battery voltage today measured 12.2 - I'm going to keep an eye on things as I know it's cold - 0 to 5 above, but that's pretty low. On the other hand, I had the hood open, the fob in my pocket when I measured so it was under a full electronics load even though not running.

I checked the connections - perfectly fine. 0 volt drop across any checked connection with lights and so on, on. Tight, clean, solid. So I can count out those connections.

 

[Biggy]

Throughout this winter I've been reading 15 v and it's always on a battery tender. Battery measures 12.7v. After a half hour or so of driving it drops to about 14.8

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