Weird starting issue 2018 Wrangler JL

[Marlowe]

Do you have any idea what is causing this?
I have attached a link to a video to show what it is doing. Both the main battery and secondary battery are fully charged. I have changed the main fuse array. I have no idea what would cause this. It starts perfectly the second time every time.
Any clue?

https://photos.google.com/share/AF1...?key=ZW5lUkxBR1hHeXVRSXVwd3JKTlNzQVhDZ0RQM1BB

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[IanNubbit]

Do you have any idea what is causing this?
I have attached a link to a video to show what it is doing. Both the main battery and secondary battery are fully charged. I have changed the main fuse array. I have no idea what would cause this. It starts perfectly the second time every time.
Any clue?

https://photos.google.com/share/AF1...?key=ZW5lUkxBR1hHeXVRSXVwd3JKTlNzQVhDZ0RQM1BB

This is normally caused by a bad Aux battery. Charged doesn't always mean good

 

[Marlowe]

This is normally caused by a bad Aux battery. Charged doesn't always mean good

I put a meter on it and it read 12.6. Is there something else I can do to test it?

 

[IanNubbit]

I put a meter on it and it read 12.6. Is there something else I can do to test it?

Not accurately. They commonly fail under load. A rough way to test would to be have a blower motor and two large lights and see what the voltagw drop is. But thats not really feasible for most people

 

[Heimkehr]

Are the batteries the original ones? Resting voltage can appear acceptable, even on an aged battery, and then drop off a cliff during cranking events.

If the batteries do date from 2018, consider replacing them to eliminate them as a potential failure point here. If the starting issues, as illustrated in your video, continue to occur after new batteries are installed, continue the diagnostic process.

 

[OldGuyNewJeep]

I put a meter on it and it read 12.6. Is there something else I can do to test it?

Do the jumperless aux bypass and see if it goes away.

 

[Reinen]

If they are the original 2018 Main and Aux batteries, thank them for the very long service life they have given you and put them out to pasture. Don't even bother testing them, they're living on borrowed time.

Always replace Main and Aux at the same time, unless you like giving the battery store extra business.

 

[Marlowe]

Do the jumperless aux bypass and see if it goes away.

Eliminating the secondary battery fixed the issue. - Thanks, everyone!

 

[BVGeezer]

Been there done that on our 2019. It was the aux battery. The symptoms of a bad aux battery very wildly. My dealer had hell diagnosing it a couple of years ago. Load tested it and did the whole nine yards and said it had to be the aux and it was.

 

[clemson]

On my 2018 Sahara JL. I did not have an aux battery. Just one large primary battery. Had to replace it at the 2 year point.

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