Possible failing alternator

[scorpionsix]

I just recently put my 2020 JLUR back into service after sitting on a consignment lot for a few months (decided to keep it after all). Ever since I picked it up, there has been a battery voltage message on the dash. It starts fine and the "dash volt meter" sometimes gets as high at 14.0 but is usually in the mid 13s. Yesterday I drove to the nearby Batteries Plus where I had purchased a H7 Duracell 750 CCA battery early this year. The battery tested fine but the tech said the alternator was weak. I didn't get the reading and am going to go to O'Reilly for a second test/opinion but this time will get the reading for the alternator. Presuming the second test/second voltmeter confirms the first test, should I in fact trust that and plan to purchase a new alternator or is there something else that might be the source of the battery voltage message. I do have the secondary battery disconnected via the negative terminal cable and fuse F42 method.

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[Penguin07]

If the second test confirms the first test of alternator being bad, then the only reason to not try replacing the alternator is if you don't trust the first or the second place, in which case might as well take it to a mechanic you do trust.
There's a lot of if this then what in your question, so just get it tested and go from there.

 

[scorpionsix]

If the second test confirms the first test of alternator being bad, then the only reason to not try replacing the alternator is if you don't trust the first or the second place, in which case might as well take it to a mechanic you do trust.
There's a lot of if this then what in your question, so just get it tested and go from there.

Basically I'm curious as to the true accuracy of those testers testing an alternator via the battery. Electricity is not my forte. The thought of purchasing a new alternator and either going through the self-install or paying yet more for a shop to install it only to find out the alternator was fine is what I'm wanting to avoid.

 

[THAW]

Ever since I picked it up, there has been a battery voltage message on the dash

A "Battery Voltage" warning and battery symbol on the dash indicates a charging system issue.

First step: check the battery terminal connectors, main body ground, and engine ground strap, plus make sure the serpentine belt isn't slipping.

Basically I'm curious as to the true accuracy of those testers testing an alternator via the battery

Many off-the-shelf alternator testers simply compare voltage to a fixed threshold, so aren't fully compatible with modern smart alternators.

JScan can be used to verify alternator functionality data - target voltage, voltage sense, and duty cycle. If there's a large gap between target and sensed voltage and/or duty cycle is maxed, the alternator is not keeping up with demand. It's also worth comparing sensed voltage to IBS voltage.

 

[Jeepy1979]

My wife had a 4 year old Chevy trax with only 50,000 kms and the alternator was shot. Had it rebuilt as it was 1/3 the price of new.

 

[scorpionsix]

A "Battery Voltage" warning and battery symbol on the dash indicates a charging system issue.

First step: check the battery terminal connectors, main body ground, and engine ground strap, plus make sure the serpentine belt isn't slipping.



Many off-the-shelf alternator testers simply compare voltage to a fixed threshold, so aren't fully compatible with modern smart alternators.

JScan can be used to verify alternator functionality data - target voltage, voltage sense, and duty cycle. If there's a large gap between target and sensed voltage and/or duty cycle is maxed, the alternator is not keeping up with demand. It's also worth comparing sensed voltage to IBS voltage.

According to the scanner the guy at O'Reilly used the battery is good, the charging system is good but the starting system cranking current and minimum cranking volts test.

Now that I'm thinking about this, even though the negative cable from the aux battery is disconnected from the main battery (along with fuse F42), I bet that thing is somehow still managing to trigger a warning message about battery voltage. Perhaps time to remove it altogether.

 

[Reinen]

If it was sitting parked for months without a trickle charger on it, the battery went through hell from parasitic draw. The JL uses battery power when parked. It would also be an odd time for an alternator to die as it's not under any particular stress when parked.

Good/Bad is a terrible indicator for a battery because they don't go from good to bad like a light switch. They get progressively worse until it reaches an arbitrary point that's called Bad. It could be on the verge of bad and still called Good.

I'd start with the battery because that was definitely stressed. Take it out and put it on a charger Repair cycle (I highly recommend NOCO chargers). 2-3 Repair cycles may be needed to break up sulfation. When repaired and fully charged, put it back in the Jeep and perform the IBS Clear/Reset procedure described here. It could be that the "smart" alternator isn't putting out full power because it doesn't think it needs to. The IBS reset will alleviate that.

You may want to get your own battery tester so you don't have to jump through the auto parts store hoops such as the TOPDON Battery Tester. It will tell you much more than good/bad and you can see how much the charger Repair cycles are helping.

 

[THAW]

According to the scanner the guy at O'Reilly used the battery is good, the charging system is good but the starting system cranking current and minimum cranking volts test.

Now that I'm thinking about this, even though the negative cable from the aux battery is disconnected from the main battery (along with fuse F42), I bet that thing is somehow still managing to trigger a warning message about battery voltage. Perhaps time to remove it altogether.

Can you post a picture of the dash message? Is the message there when the engine is on or off (or both)?

 

[scorpionsix]

Can you post a picture of the dash message? Is the message there when the engine is on or off (or both)?

I'll take a pic but it literally says Battery Voltage and nothing else. No warning lights though. I'll toggle through the three ignition settings and confirm when the message displays - aside from when the vehicle is running.

 

[THAW]

I'll take a pic but it literally says Battery Voltage and nothing else. No warning lights though. I'll toggle through the three ignition settings and confirm when the message displays - aside from when the vehicle is running.

On a red background? No battery symbol?

 

[scorpionsix]

On a red background? No battery symbol?

Just the two words with no colored background and no symbol. I'm going to reset the IBS when I get home to see if that clears the message.

 

[THAW]

Just the two words with no colored background and no symbol. I'm going to reset the IBS when I get home to see if that clears the message.

Did the consignment lot just switch your EVIC to page 2, submenu 7, the Battery Voltage screen?

 

[scorpionsix]

Did the consignment lot just switch your EVIC to page 2, submenu 7, the Battery Voltage screen?

Problem resolved: I'm straight up stoupiiiiiiid. Clearly I'm ingesting way too much artificial sweetener on a daily basis and brain rot is setting in. While something is triggering an issue on the parts store scanners - two now, the "message" is one of the standard labels. When I first picked up the vehicle, the voltage was reading low, around 13.5, and I immediately mistaken the label for a warning message. I was trying to reassociate myself with the layout of all the buttons, knobs, infotainment system and dashboard data and wasn't used to/forgot about certain things.

Having said that, it's time to pop open my daily can of zero-sugar Monster and resume brain rot operations.

 

[THAW]

...something is triggering an issue on the parts store scanners - two now...

Low voltage during a successful crank is usually an early sign battery health is declining - especially when the engine and/or ambient temperature isn't cold.

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