XJNBREWS

Ever since i have had my XJ (For 1.5 years now) the voltage gage on the dash has read always slightly above 14V (~14.1/14.2), but i recently have noticed it is now reading very close to 15V. keep in mind the temperature here is -7F and with windchill it is -30F, but i am concerned i have a problem and unsure of what the problem could be.
The battery and alternator has not been changed since i bought the Jeep, but had no reason to replace...
all electronics are working as they should, nothing is staying on or acting abnormal.
no check engine light, no change to wiring of anything.

boxburn

Have you checked the voltage at the battery to confirm the gauges reading?

XJNBREWS

no, but i will tonight and let you know. lets say it checks out correct, then what would be my issue? or is this normal due to the cold weather? normally when weather is above freezing or warm out it is back to 14.1/14.2

boxburn

I'd have to have a look into it myself to work out what could cause it or someone else who knows more could assist. Hopefully it's the gauge giving you a false reading.

jordan96xj

Definitely do a system voltage test at the battery (with vehicle running) so that we know whether there is a discrepancy with the gauge.

It definitely will be higher when the temperatures are colder, this is a function of the temp sensor that sits under the battery.

I can tell you that my internal voltage (as measured in the cab, via the OBD2 diagnostic port) is about 13.5 - 13.8v in this freezing temps we are having. Given that the cab voltage usually runs a little lower than the actual system voltage (about 1v lower in my case). The numbers you mention are not that far off. However, the fact that your internal gauge is close to 15v, that does give some concern that things might be higher than they should be. This is sometimes caused by a faulty battery temperature sensor, but can also be caused by a PCM that is sensing voltage lower than it actually is because of a poor connection. So it basically commands the alternator to produce more voltage than it should.

But don't overthink it until you get that reading at the battery. That is the real fact. Not the gauge.

XJNBREWS

jordan96xj

What year is the vehicle?

For a modern vehicle that would be about right. But something tells me that might be on the high side for an XJ (but maybe not, given the cold we are seeing). If we can cross check against the FSM, we could probably see if that is within spec for the year (different years can tolerate different levels of voltage within the various components).

XJNBREWS

jordan96xj

So I have the 97 FSM, and it says that previous years were a bit different, but that it's normal range would be 12.9 to 15v. So based on the condition of the battery and just how cold it is, I'm not sure that there is a problem here. Especially given that you always had 14.1ish and now you are seeing 14.7ish in the brutal cold. That is about the same change I am seeing in my 96 (relatively speaking). Mine went from about 12.9 in the warm months to being about 13.7 right now in sub-zero temps.

Part of what can make you voltage higher is how much your battery is needing to be charged. So I don't know the condition/age of your current battery, but you may find with a new one that the voltage level is high just until the battery is fully charged and then settles down to a more reasonable level. So I guess I'm saying, that higher than normal voltage could be a warning that your battery is never reaching a state of fully charged.

XJNBREWS

I appreciate all the feedback, I’m sure I’m due for a new battery as I have no clue how old it is. Anyway, it’s good to know that my voltage is still OK.

GreaseMonkey17

firebane

The battery has a sensor of which the vehicle uses to determine more or less voltage.

GreaseMonkey17

firebane

Look under the battery you will see a small black puck. It's what allows the pcm to alter the voltage.

I forgot to okug mine back in and it wouldn't charge past 13.7 vokts

GreaseMonkey17