Saw 15.3 volts today

[ShadowsPapa]

Pulled into a parking lot and saw 15.3 volts - that's .3 higher than I've ever ever seen on a Jeep before.
Just as I pulled into the parking spot - I swear the radio "blinked" - a fraction of a second it was black then came right back

Also after done in the store, I started the jeep, saw a song on the radio I wanted to hear, used the steering wheel button 3 pushes to increase volume and it kept climbing and maxed out volume - no way to reduce it for several seconds. My wife asked "what the hell are you doing!" - I said nothing - it's doing it by itself!

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[MPMB]

you didn't happen to leave a wrench under the hood, did you?

 

[ShadowsPapa]

you didn't happen to leave a wrench under the hood, did you?

No and I didn't even get to 75, let alone 88 mph

 

[Bandit’s Lair]

Have you done any electrical lately? I remember seeing you had a pretty involved system for electronics on there. Maybe something got crossed. Or was there a solar flare?

 

[ShadowsPapa]

Have you done any electrical lately? I remember seeing you had a pretty involved system for electronics on there. Maybe something got crossed. Or was there a solar flare?

Nothing at all under the hood or even dash. First thing I will check is the connections at the batteries. For a fluctuation that large, that big a spread, and voltage that high - yeah, I'm going to wait until it's warm enough to open the shop door again and run it in and check connections.

 

[Bandit’s Lair]

Yeah that’s a heck of a jump. Mine has finally settled into 12.7-12.8V consistently. 15 is like it got water sprayed on it or something to cause a quick flash. I’m surprised nothing fused out.

 

[OVERLORD]

you didn't happen to leave a wrench under the hood, did you?

You didn't happen to leave a wench under the hood, did you?

 

[mtudb24]

Nothing at all under the hood or even dash. First thing I will check is the connections at the batteries. For a fluctuation that large, that big a spread, and voltage that high - yeah, I'm going to wait until it's warm enough to open the shop door again and run it in and check connections.

Papa, if you remember my issue when it hit 15.0V and higher yet the voltge at the battery was still 12.7 / 12.8, that pack of 3 battery cables on the positive post and terminal closest to the firewall was ever so slightly loose. Tightening that cable took care of all those gremlins I had with the dash lights coming on for traction control, stability control, ABS warnings, AC stopped blowing, exterior lights flickering, etc.

I would definably check that connection for sure. I have had tighten it twice in the last 6-9 months and finally put blue lock tight and its never been an issue again.

 

[Chaos Theory]

Solar storm.

 

[ShadowsPapa]

Papa, if you remember my issue when it hit 15.0V and higher yet the voltge at the battery was still 12.7 / 12.8, that pack of 3 battery cables on the positive post and terminal closest to the firewall was ever so slightly loose. Tightening that cable took care of all those gremlins I had with the dash lights coming on for traction control, stability control, ABS warnings, AC stopped blowing, exterior lights flickering, etc.

I would definably check that connection for sure. I have had tighten it twice in the last 6-9 months and finally put blue lock tight and its never been an issue again.

Definitely my first things to check!

 

[tysongladiator]

In my opinion, I FEEL like @mtudb24 is close to what your issue might be. A loose connection would give a false reading to the alternator that the battery is low so the alternator is working harder trying to charge the battery. For me, it was the negative battery cable terminal. I had to put a shim in it to get the connection tight to fix the issue.

So, I would definitely check that connection and all connections.

 

[Rahkmalla]

Solar storm.

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.

 

[WILDHOBO]

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 strikes, 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.

If that works, maybe you standing there at all isn’t a great idea.

 

[ShadowsPapa]

In my opinion, I FEEL like @mtudb24 is close to what your issue might be. A loose connection would give a false reading to the alternator that the battery is low so the alternator is working harder trying to charge the battery. For me, it was the negative battery cable terminal. I had to put a shim in it to get the connection tight to fix the issue.

So, I would definitely check that connection and all connections.

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.

 

[Mr Miami]

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 strikes, 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.

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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