URGENT help needed. Can't start my 2018 JL

[kantho]

2018 JL Sport S with the 3.6. Got in this morning and the needles for the speedo and tach were twitching. I push the start button and all inside lights and dash flashed on and off but no start. Tried charging the battery awhile and next attempt to start even the wiper (turned off) started wiping.

Is this some code for something? Is the JL light flashing trying to tell me something? Is there a master switch somehow where I can reset the electronics?

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[Zandcwhite]

The 3.6 uses an auxiliary starting battery, hidden under the primary battery. They seem to not respond well to charging or jump boxes, but people have had decent luck with traditional jump starts from a running vehicle with jumper cables.

 

[James_a]

I had a similar issue. If the voltage is too low and you tried an older AGM charger/maintainer it may not recognize the battery and start charging. That's what happened to mine. I hooked it up to jumper cables and let it sit for 15-20min on another truck and it started up just fine. After getting the voltage back up the maintainer worked without an issue. Since then I haven't had a problem but I did buy a new maintainer that will charge a battery down to 1v just in case...

 

[Jebiruph]

2018 JL Sport S with the 3.6. Got in this morning and the needles for the speedo and tach were twitching. I push the start button and all inside lights and dash flashed on and off but no start. Tried charging the battery awhile and next attempt to start even the wiper (turned off) started wiping.

Is this some code for something? Is the JL light flashing trying to tell me something? Is there a master switch somehow where I can reset the electronics?

It looks like your batteries were almost completely drained and you need to keep charging for a while longer to get them recovered enough to start.

 

[kantho]

The 3.6 uses an auxiliary starting battery, hidden under the primary battery. They seem to not respond well to charging or jump boxes, but people have had decent luck with traditional jump starts from a running vehicle with jumper cables.

So you're saying the flashing dash means low battery?

 

[James_a]

Electronic systems going crazy have been seen when batteries are low. when I first tried starting mine my windshield wipers tried turning on and my dash was going crazy... If you have a tester do a quick check of the voltage.

 

[Zandcwhite]

So you're saying the flashing dash means low battery?

Yes

 

[Jebiruph]

So you're saying the flashing dash means low battery?

With virtually dead batteries very little happens, but there there seems to be a threshold when there is enough of a charge for the electronics to attempt to function, but fail.

 

[kantho]

I had a similar issue. If the voltage is too low and you tried an older AGM charger/maintainer it may not recognize the battery and start charging. That's what happened to mine. I hooked it up to jumper cables and let it sit for 15-20min on another truck and it started up just fine. After getting the voltage back up the maintainer worked without an issue. Since then I haven't had a problem but I did buy a new maintainer that will charge a battery down to 1v just in case...

So what is the correct battery type for the JL? My charger has STD, AGM or GEL/

 

[kantho]

The 3.6 uses an auxiliary starting battery, hidden under the primary battery. They seem to not respond well to charging or jump boxes, but people have had decent luck with traditional jump starts from a running vehicle with jumper cables.

How do I access this aux battery to check its charge level and connections?

 

[Zandcwhite]

How do I access this aux battery to check its charge level and connections?

It’s mounted under the fuse panel, you have to take the main battery and fuse panel out for access. If you just want to test it’s voltage, the leads run up to the main battery. Disconnect main battery positive and negative and you’ll read the voltage of the auxiliary battery between the leads. Dangerous, foolish, terrible design as you still have voltage from a hidden battery source even if you completely remove the main battery from the vehicle.

 

[Arterius2]

So what is the correct battery type for the JL? My charger has STD, AGM or GEL/

AGM

 

[James_a]

Before you start pulling things apart check the voltage of them combined. Just test off the main battery. If it's low use jumper cables then top it off when the voltage is high enough. That should do unless your battery is bad. Which you'll know if the problem persists. If the problem is still there then consider taking it in under warranty. If out of warranty then pull it apart.

I considered pulling the aux battery but at least for myself it wasn't necessary.

 

[kantho]

Before you start pulling things apart check the voltage of them combined. Just test off the main battery. If it's low use jumper cables then top it off when the voltage is high enough. That should do unless your battery is bad. Which you'll know if the problem persists. If the problem is still there then consider taking it in under warranty. If out of warranty then pull it apart.

I considered pulling the aux battery but at least for myself it wasn't necessary.

Are the 2 batteries wired in parallel? I disconnected the ground from the visible battery and have been charging it quite awhile. Now connecting the charger to the negative battery cable isolated from the top battery and will try and charge that.

My Jeep is under warranty but I suspect that excludes the battery. I also have a ZAutomotive Tazer Lite installed and can't unmarry it without power which is what I'm supposed to do before taking it to the dealer.

 

[JimLee]

Unfortunately many people have only been getting about 2 years out of the stock batteries before they go to shit, you may be there. If you have to replace, replace both of them.

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