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Voltage Gauge read 19 volts - Digital Meter says 14.2

Is there any risk to the electric circuits driving with this high a voltage?

Excessive charging voltage can burn up any 12 volt component or 5 volt OBD-II sensors. This includes the PCM, TCM, and the am/fm stereo.

If all diagnostics and trouble shooting is negative, the very last thing to suspect is failure of the voltage regulator circuits inside the PCM.
 
Tim, Thanks for the check list. I have confirmed most of these already. Not long ago I replaced all my heavy gauge cables. In general I keep my rig well maintained. I'm always being accused of having to "clean of a Jeep" :)

CLS, I have not been driving the XJ in fear of burning up circuits. In my 30 years as an IT analyst, I have seen many weird things just come and go with no reason. I refer to this as the Pixie Dust solutions.

Is there any risk to the electric circuits driving with this high a voltage?

It’s not high, the computer is being stupid. When I had my issues, I had a digital voltmeter hooked to the battery and it was solid 13.8 volts.
 
Why? My battery is hooked to the alternator by 1/0 gauge cable. If anything, PCM would show lower voltage.

You could have a bad ground from the battery to the chassis, it's best to check for codes and see what voltage the pcm is seeing.
 
The Yellow Top had shorted internally. Replacing the battery fixed the issue.


Did the voltage tests (post 2 post, running idle) read proper on that yellow?


I do have a blue top. But it's showing 12.7 P-P.
Maybe I'll swap out a newer red I have in the CJ to see if that makes a difference.
 
Excessive charging voltage can burn up any 12 volt component or 5 volt OBD-II sensors. This includes the PCM, TCM, and the am/fm stereo.

If all diagnostics and trouble shooting is negative, the very last thing to suspect is failure of the voltage regulator circuits inside the PCM.


That was fully suspected early on. So I swapped in my brand new spare PCM.
Didn't make any difference. Both PCM's are telling the generator to output over 19v to the charging system. Thinks it has some great load.


Also when I load it down with everything I got. The gauge will center out.
Ass soon as I turn the lights, or AC off, it pegs out again.
Here is a good example of the behavior:


https://www.youtube.com/watch?v=5Vw-D6ulWcI
 
You could have a bad ground from the battery to the chassis, it's best to check for codes and see what voltage the pcm is seeing.


I am suspicious of this being a grounding issue. By codes are you referring to the check engine light error (OBD-II) codes? I'm not getting any.
I saw someone mentioned scanning the BTS via the OBD. Perhaps I need to understand my reader better. See what it will see while the engine is running.
 
If the dashboard voltage gauge shows 19 volts, there almost always a connectivity issue, most often corroded battery lugs/terminals, internally corroded battery wires, or a loose connection in the charging system. The PCM does not see correct charging levels due to the poor quality connections, and it thinks the voltage needs to be full blast.
 
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Did the voltage tests (post 2 post, running idle) read proper on that yellow?


I do have a blue top. But it's showing 12.7 P-P.
Maybe I'll swap out a newer red I have in the CJ to see if that makes a difference.

I don't think I ever put a multimeter on it. I do remember coming out to a dead battery. To jump it, we had to disconnect the battery terminals and jump off the cables alone. When we put the cables back on the battery it showed 19V. The headlights and interior lights were not brighter than normal so I doubt the voltage was as high as the gauge read. Replacing the battery with a decent Auto Zone Gold battery fixed the issue.

After that I noticed other places I'd go would have stacks of Optima batteries and everyone said the same thing - they'd never buy another one. It seems like the original Optima's were good batteries. I bought one because the 3/4 ton Dodge Cummins had one that was 9 years old and still worked. But by around 2007-2008 the quality had plummeted. Apparently when they moved the plant to Mexico they had a bunch of QA issues that were supposedly fixed. I just buy the Auto Zone ones anymore. There are lots of Auto Zones and Auto Zone typically has the best (longest) hours. They fail within a couple of years usually just inside the pro-rated warranty so I get a new one for free.
 
If the dashboard voltage gauge shows 19 volts, there almost always a connectivity issue, most often corroded battery lugs/terminals, internally corroded battery wires, or a loose connection in the charging system.


Today I'm going to take a closer look. Makes sense the voltage would spike if there is a bad ground or fault somewhere. I bet you would bet me on the main cables.
 
I quit buying the yellow tops. My CJ ate those things up. I thought they would be best for the winch. I have had excellent luck (so far) with the blues with winches. I too have gone to NAPA batteries and parts in general for that matter. I will only go to AZ, O'R, etc. for oil and paper towels.
 
So after cleaning all the cables and connectors, testing everything I could think of, I finally took it into my local Auto Electric shop. Turned out to be the Alternator. I didn't test this because I had just replaced it 3 months prior. Figured I could rule it out. Nope. Brand new NAPA alternator faulted inside. $400 later all is good.
 
Well I would have lost that bet, since an internally shorted alternator is very highly uncommon, but not the first one I have heard about.
 
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