AUX BATTERY

agpthng

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I have a 2019 JLU Sport S and recently I'm getting some weird messages across my screen, check engine, start stop system failing, ess, shifter, abs. While sitting in line yesterday at McDonald's drive through everything went haywire - speeedometer bottomed out, it was surging, put it in park and then couldn't get it out of gear, it shut off then started back up - 4 way flashers barely worked. We had bought a new main battery the day before, so went home and put that in. Called the dealer this morning to have them replace the aux battery and the lady said it's under the driver's seat. Funny the manual shows it under the main battery.

 

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The aux battery is directly under the engine bay fuse box. The easiest way to get to it is by removing the inner fender, you'll see a square compartment with I think 4 bolts and the battery bucket will then fall on your head. I just installed a Genesis dual battery to get rid of that stupid aux battery. If you're a 2019 you're pretty much due for one. I went from the top down, though, which requires removing the entire fuse box and its bus bars/etc. Those messages are pretty indicative of a dead aux battery.

If you look in the Tech forums there's a battery/electronic subforum that is probably 80% of us complaining about aux batteries, go check that out for better details. Theres a few threads about removing a jumper to bypass the aux altogether.

https://www.jlwranglerforums.com/forum/forums/battery-talk.195/
 
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agpthng

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The aux battery is directly under the engine bay fuse box. The easiest way to get to it is by removing the inner fender, you'll see a square compartment with I think 4 bolts and the battery bucket will then fall on your head. I just installed a Genesis dual battery to get rid of that stupid aux battery. If you're a 2019 you're pretty much due for one. I went from the top down, though, which requires removing the entire fuse box and its bus bars/etc. Those messages are pretty indicative of a dead aux battery.

If you look in the Tech forums there's a battery/electronic subforum that is probably 80% of us complaining about aux batteries, go check that out for better details. Theres a few threads about removing a jumper to bypass the aux altogether.

https://www.jlwranglerforums.com/forum/forums/battery-talk.195/
Thanks - odd that the dealer is telling me it's under the seat.
 

Rhinebeck01

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@agpthng

Dealership Service Dept. will be the one that decides if either one or both batteries are "dying" and needs replacement.

When you bring the JL into the dealership, politely tell the Service Writer you'd like to speak to the Service Manager. Again, ask to speak directly with the Service Manager.

Tell the Service Manager you have heard good things about his/her Service Dept., yada yada... YES, swooze him a bit...
......Then politely ask that they LOAD TEST the battery on your JL and that they provide you with a copy of the print out of the LOAD TEST results for your personal records.

Without the load test results you will not be sure the Tech actually Load Tested your JL's battery.. He might just charge up the battery, never load test it and send you on your way...


It will take the Tech about 2 hrs. total to properly load test the battery. He had to fully charge the battery and then do the load test.... and do his load test print out.

Also... if the dealership does replace your battery, that replacement battery only has a one year warranty on it.
 


TheNewGuy

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Thanks - odd that the dealer is telling me it's under the seat.
Dealer may be confusing aux battery with eTorque battery which is on the undercarriage under the rear seat
 
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agpthng

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Hoping this isn't a costly thing! I can't remember if I bought the extended warranty or not but it is what it is and needs to be fixed. Appt. at the dealer for 8/25 - hope it stops misbehaving between now and then.
 

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I can speak from recent experience that your main was most likely bad but it is wise to do both batteries. Your aux is probably draining the main. I would suggest disabling the aux as many of us have and not worrying about it anymore. If you do this you have to remember to disable the start/stop every time, purchase a tazer or purchase a smart start/stop eliminator. You can pull fuse F42 which is for the PCR for the start/stop system and remove the negative terminal for the aux battery, tape it off and zip tie to the other cables. @Rhinebeck01 is very knowledgeable about these systems and I highly recommend listening to his advise as well.
 

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Do not replace the aux battery by going through the fuse box. follow the factory procedure manual and go through the fender well. Two bolts the box drops down the battery gets changed. Super Simple.
 


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agpthng

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Update: The dealer replaced the aux battery yesterday, not under warranty, it's a maintenance thing but should have lasted closer to 5 years not 3. $374 later.
 
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agpthng

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Ouch. I did mine and the battery was about $100 and at most 30 minutes of labor to do it myself.
I guess it was an hour, hour and half. If we were able to would've done it ourselves, but my husband's health at the moment isn't allowing him to do stuff like that after back surgery.
 

Bryce

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Update: The dealer replaced the aux battery yesterday, not under warranty, it's a maintenance thing but should have lasted closer to 5 years not 3. $374 later.
Ya, batteries fall under 3yr/36,000. If you are over that, its on you.
 

Chupacabra

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Ya, batteries fall under 3yr/36,000. If you are over that, its on you.
Mine was under warranty but I just didn't want to deal with taking it in to the dealer, getting rides to/from the dealer, then risking having them tell me nothing is wrong on top of that. Was just easier to do it myself and get it over with...

 

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