Help....Electrical?

[DanW]

A buddy who just bought a 2020 JT Overlander had his dash light up like a Christmas tree (see photo). It stranded him and would not start....wouldn't even engage the starter. The interior lights and everything went wonky. It was giving the message in the photo and also a power steering message of some sort, but others, too. I immediately thought battery, because his batteries were 4 years old. So we swapped out both the big battery and the aux battery and it started right up and acted normally. We thought we nailed it. This morning he didn't get very far when it lit up again.

Any ideas? Has anyone seen this before? The only consistent thing is the power steering warning/message.

Any help is appreciated!

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[jebiruph]

Check for a blown N3 fuse. If it's blown, the aux battery isn't getting charged.

 

[Badweather]

Are they the original batteries

 

[DanW]

Check for a blown N3 fuse. If it's blown, the aux battery isn't getting charged.

Awesome, we will check that! IT was doing fine for a short while and then lit up again, so that would make sense, based on the behavior of the vehicle.

 

[DanW]

Are they the original batteries

Yes, originally. We swapped out both the aux and main batteries last night. His original batteries were 4+ years old. I've seen a number of JL's and JT's that acted wonky like this and replacing both batteries cured it. My cousin's 2018 JK, which is a single battery non-ESS setup did the same when his battery failed. He thought his whole electrical system failed.

Interestingly, my JT had its aux battery fail. It did what it should and just disabled ESS and gave me a message on the dash. The dealership replaced both under warranty at 35,500 miles. Lol, dodged one there! I marked November 2026 as the 3 year replacement date for those batteries. Last thing I want is one of these things crapping out in the middle of a trail somewhere.

 

[Badweather]

Did new batteries fix it

 

[DanW]

Did new batteries fix it

For a a very short distance. Maybe 10 miles. I think that is why that N3 fuse is now suspect. It is behaving as if one of the batts is not charging.

 

[Badweather]

Make sure your new batteries we’re fully charged when you installed them

 

[DanW]

Make sure your new batteries we’re fully charged when you installed them

Good suggestion. He was told they were fully charged but I doubt stores really check that. I should've brought my charger over when I went to help him install them last night. I've got a nice little Optima 400 charger that would have told us pretty quickly their condition.

Not sure what he's doing with it right now...he may have towed it to a dealership. But if he got it home, I'll take that charger over there this evening.

 

[DanW]

I just sent him a text. It looks like he took it to a local dealership. It's a dealer whose service department has a pretty good rep. Hopefully they'll get a quick diagnosis.

Right now I'm still betting on something like the N3 fuse being blown. I've seen a bunch of JL/JT batteries get replaced from Autozone or Advance Auto and haven't seen any issues with them not being charged. That said, I don't think they check them. It's also entirely possible to get a bad one, even though I've not experienced it.

 

[Badweather]

From a battery store they will not be fully 100% charged I guarantee it, I would guess around 90% which is enough for most vehicles. However, in our Jeeps especially when you are replacing its good to have them at 100% via a trickle charger and make sure the IBS was disconnected for at least 5 minutes

 

[punk'n]

I don't think I've ever bought a battery that was at 100%.

In fact, I literally just bought a brand new battery this morning directly from a battery distributor (not an auto parts store). As soon as I got home I put a meter on it and it was 12.1 (50-60%). I now have it charging.

 

[DanW]

Yeah, we should have checked them. It was late at night and we were trying to get it knocked out. Maybe the dealership will figure out they just need charged and will get that done.

But again, I've been involved in the replacements of about 4 of these....mostly JL's, but also a JT, and the store bought batteries worked just fine without a charge. But with this one having a big error and shut down, maybe it didn't reset. Although we did have batteries fully disconnected for probably 1/2 hour or so.

 

[Istvanwalker]

Yes, originally. We swapped out both the aux and main batteries last night. His original batteries were 4+ years old. I've seen a number of JL's and JT's that acted wonky like this and replacing both batteries cured it. My cousin's 2018 JK, which is a single battery non-ESS setup did the same when his battery failed. He thought his whole electrical system failed.

Interestingly, my JT had its aux battery fail. It did what it should and just disabled ESS and gave me a message on the dash. The dealership replaced both under warranty at 35,500 miles. Lol, dodged one there! I marked November 2026 as the 3 year replacement date for those batteries. Last thing I want is one of these things crapping out in the middle of a trail somewhere.

Exact same thing happened to me last week when replacing both batteries. Something got shorted out and the issue turned out to be the high amp fuse array. $95 at the Chicago Jeep dealer. Simple install.

 

[DanW]

Exact same thing happened to me last week when replacing both batteries. Something got shorted out and the issue turned out to be the high amp fuse array. $95 at the Chicago Jeep dealer. Simple install.

Is that the Z-pack, I think it is called? That's where the N3 is located.

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