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. It starts up without hesitation but if the starter is in fact the issue, would that trigger a battery voltage message?

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