Battery / alternator over voltage

[MSteber]

2005 Jeep TJ.
Rubicon
6 speed manual.
66000 miles

Noticed with engine running, voltage at battery is 15.5 V.

With engine not running, voltage at battery is 12.5V.

Charging system Gauge on dash shows 14V.

No check engine light.



Did multiple searches on this topic and tried the following.

1 cleaned both positive and negative battery terminals.

2 cleaned ground connection at battery- goes to chassis center bolt on firewall. And alternator.

3 cleaned chassis ground connection located on center bolt of firewall

4 cleaned ground connection at alternator.

All resulted in no change.

Voltage is still reading 15.5V


Note- there is no check engine light on.

There are no noticeable performance issues.


As I understand it, the alternator output is set by multiple parameters including engine load, battery charge level among others.



Any suggestions?

Would replacing alternator fix this or do I need to address this with PCM fix?

Should I consider external voltage regulator?

I plan on checking engine ground.



With no observable performance impacts, is there a problem with leaving things as is?

Will alternator life be reduced.

Will battery life be reduced?



Thanks in advance.

 

[DuckNut]

It is not uncommon for it to produce 15v when it is cold. What is the output when at normal operating temp?

What device are you using that shows 15? Is this hooked up to something different than the dash gauge? Is your instrument out of calibration? Is the gauge out of calibration?

I would think that if you are reading after the PCM you would be getting the same as the gauge. Maybe not true if you are reading before the PCM as that controls the voltage.

PCM ... ECM... Whichever, the voltage is controlled by the cars computer.

 

[macleanflood]

Do you have a battery temperature sensor?

-Mac

 

[MSteber]

Thanks for the comments.
I used 2 different multi meters.
Both showed the 15.5.
That reading was made at the battery with engine running.
When engine is not running, both read in the 12.5 V range.

Not sure how to calibrate dash gauge.

Note the outside temperature is in the high 30s to mid 40s (F). I have not considered that.

Background, I didn’t even realize I had this condition until I installed an Audio amplifier. One installed it kept going into protect mode.

After some troubleshooting, this 15.5V condition was found.

I just learned about the battery sensor. I will have to check that, but I thought I read in this forum that item was removed from this model year -2005.


Can you really reset pcm by removing negative battery terminal for 10 minutes.


Thanks for the help.