Aftermarket alternator?

[Whaler27]

My 2019 JLUR with the 3.6 just killed it’s second pair of batteries since I installed the Genesis dual battery system less than 10,000 miles ago. The jeep has less than 15,000 miles on it, so it’s spent most of its life in my shop on a Noco smart charger.

Last week the check engine light came on, so I connected a diagnostic tool to the OBD port to read and clear the code. The code was insignificant and unrelated to the electrical system, but I decided to do a full diagnostic run while I was hooked up. One of the diagnostic routines is an alternator check. The code reader tracks the jeep at idle for a while, then it instructs you to bring the RPMs between 2000 and 3500 rpms for about 30 seconds, than back to idle. The report said my alternator is in bad shape.

The OEM alternators are stupid expensive. Anybody had good luck with Napa alternatives? They have worked great in other vehicles, but some say Wranglers are too finicky. Thoughts?

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[Left Field]

A failed alternator at 15k miles is a bit unusual indeed. I wonder if the OBD diagnostic takes into account the 'smart' charging algorithms that our Jeeps use, which move the voltage level around anywhere between the mid 12's to the mid 14's however they see fit.

What voltage range do you see on your dash display while driving?

You might consider taking your alternator into NAPA and have them bench test it. That might give you a better indication of its health by taking the Jeep's 'smart' functions out of the equation.

Other follow-on possibilities might be parasitic draw or even a problem with the NOCO charger.

LF

 

[THAW]

Which diagnostic tool?

With JScan you can track alternator duty cycle, target voltage, and sensed voltage to see what's actually happening with the alternator.

MODULES -> Powertrain Control -> LIVE DATA ->
Generator Duty Cycle (%DC)
Target Charging Voltage (V)
Voltage Sense (V)

 

[mwilk012]

Dumb old tools can’t be used to properly diagnose an alternator anymore. Half the time they’re not charging and that’s intentional operation.

 

[ChoSunJuan]

Mean Green alternator are pretty good.

Jeep Alternators https://share.google/aGI1qP8nWiuFrPSjC

 

[58Willys]

Before condemning or replacing the alternator; I’d carefully check all your cables, connections, grounds, etc… Also test your IBS. Are the batteries holding a charge after charging with the NOCO?

 

[Hard Rock Jeep]

As noted above, beware of auto parts stores devices telling you your alternator is bad. A buddy with a JL with the mild hybrid option was told by one store that his alernator was bad. That model does not have an alternator. Some may have reliable devices, others don't.

I have a JK with significant electrical upgrades. I was going thru batteries every 12 months. I installed a Mechman alternator and have had zero issues for several years. (Thinking...should I have said that...)

If you have an automotive electrical shop nearby, they can most likely help you.

 

[Left Field]

An interesting read regarding NOCO chargers and AGM battery failure. FWIW.

https://marinehowto.com/noco-chargers-no-go/

That said, I've not found any charger/maintainers that I'm 100% happy with.

LF

 

[THAW]

An interesting read regarding NOCO chargers and AGM battery failure. FWIW.

https://marinehowto.com/noco-chargers-no-go/

That said, I've not found any charger/maintainers that I'm 100% happy with.

LF

The NOCO charger referenced in that article/"post" is very old (discontinued) and the performed test is on a LiFePo4 battery. The article/"post" is essentially an out-of-date, confusing mess.

Which is not to say current NOCOs are perfect chargers. But I can't imagine them still letting healthy lithium batteries drop below 12.5 Volts.

For reference, the tests performed by a member of the JT forum on the more modern NOCO 10 show the AGM profile kicking in consistently whenever the battery dropped below 12.875 Volts.

 

[Whaler27]

A failed alternator at 15k miles is a bit unusual indeed. I wonder if the OBD diagnostic takes into account the 'smart' charging algorithms that our Jeeps use, which move the voltage level around anywhere between the mid 12's to the mid 14's however they see fit.

What voltage range do you see on your dash display while driving?

You might consider taking your alternator into NAPA and have them bench test it. That might give you a better indication of its health by taking the Jeep's 'smart' functions out of the equation.

Other follow-on possibilities might be parasitic draw or even a problem with the NOCO charger.

LF

You may be right. The diagnostic tool asks for make, model, year, and engine. It monitors for about 90 seconds, I think, while directing you to maintain certain RPM ranges. Given that, I assumed it had model-specific checks that accounted for unusual programming, but maybe not. I also wondered whether the dual battery recharge power pull was absorbing too much juice. (I don’t know what sensors the OBD system is reading/comparing).

Dumb old tools can’t be used to properly diagnose an alternator anymore. Half the time they’re not charging and that’s intentional operation.

The tool I was using is an Innova 5610. It’s supposed to be pretty skookum. Maybe not?

 

[THAW]

The tool I was using is an Innova 5610. It’s supposed to be pretty skookum. Maybe not?

I don't think the Innova 5610 alternator test is compatible with PWM alternators.

"Note: Do not perform this test on Smart Alternator..."

 

[mwilk012]

The tool I was using is an Innova 5610. It’s supposed to be pretty skookum. Maybe not?

There is NO tool that can just clip on to a battery and tell you if an alternator is bad based on a charge/no charge condition. At best, it can tell you whether or not it is currently charging. Now testing for AC ripple, yea that works, but that’s very rare anymore.

 

[THAW]

There is NO tool that can just clip on to a battery and tell you if an alternator is bad based on a charge/no charge condition. At best, it can tell you whether or not it is currently charging. Now testing for AC ripple, yea that works, but that’s very rare anymore.

Technically, the tool he has plugs into the OBD-II, so theoretically it could assess smart alternator performance to some degree. But I believe all it does is monitor voltage while the user switches on the headlights and revs the engine, so in most cases it doesn't actually collect meaningful information about a JL alternator.

 

[mwilk012]

Technically, the tool he has plugs into the OBD-II, so theoretically it could assess smart alternator performance to some degree. But I believe all it does is monitor voltage while the user switches on the headlights and revs the engine, which means it doesn't actually collect any useful information about a JL alternator.

That’s even worse then, the measured voltage at the obd port is unreliable as hell. Our scan tools regularly read a half volt low. Retrieving the system voltage data pid from the PCM is better, if it’s doing that, but then you’re totally losing the ability to measure for AC voltage.

 

[Whaler27]

Technically, the tool he has plugs into the OBD-II, so theoretically it could assess smart alternator performance to some degree. But I believe all it does is monitor voltage while the user switches on the headlights and revs the engine, so in most cases it doesn't actually collect meaningful information about a JL alternator.

Correct. It’s plugged into the OBD port. I don’t know where it pulls it’s data from, but the analytical process takes quite a while. Since I don’t understand how automotive computers work, I’m skeptical. On the other hand, the new batteries need to be plugged in most of the time, even when the jeep is driven 30 to 40 minutes three or four days per week, although there is very little parasitic drain (mostly from the Genesis relay, I think).

The Innova 5610 has to be set up to read each vehicle. If it’s set up for, say, a Ford truck, then plugged into the Jeep OBD port, it won’t be able to connect, because it's speaking a different language or looking for different readings. When you properly enter year, make, and model, it asks which engine you have — so it “knew“ it was connected to a 2019 Wrangler with the 3.6, and it cycled through all the vehicle system checks. Maybe it’s just a light show?

I think I’ll give the guys at Genesis a call. I had hoped to upgrade to their new top plate, as the new system has almost zero parasitic drain, but it’s $500, bringing the total genesis and battery cost to about $2100… There is no discount for folks who have been suffering with the original Genesis system for years. (I was hoping there might be a $200 or $250 rebate for returning the old top. They’d still probably be making $150 or $200 on the sale. No such luck, so I’m reluctant to bend over and grab my ankles.)

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