2018 JLU Aux Battery problem

[Jebiruph]

With a properly functioning system, the main battery and aux battery are wired in parallel except when auto stopped. If something is draining the aux battery and not the main battery, the batteries are no longer in parallel. A blown N3 fuse breaks the parallel connection between the batteries and prevents alternator power from charging the aux battery and powering the system electronics. The system electronics run off of the aux battery until the aux battery is drained.

You can verify a blown N3 fuse by a lack of voltage at the N3 terminal and you can move the wire from the N3 terminal to the N4 terminal to restore the connection from the alternator to the aux battery and the system electronics.

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[Tiger4Life]

It sounds like your N3 fuse is blown and if that's the case, you can move the wire from the N3 terminal to the N4 terminal to get power back to the system electronics.

Thanks Jeb. I am waiting to hear back from my mechanic. I would think they checked the fuses, but I could be wrong. They are a really good shop, and I would not let anyone else touch it except them. Dealer said that they couldn't get to it for 3 weeks, so he was going to talk with the Jeep people about bypassing the aux battery.

 

[Tiger4Life]

Update: I have spoken to my mechanic and Jeep wants to replace the entire PCB. I asked him to change the high amp bar next to the battery since it’s possible that the N3 or N4 fuses could be blown. So we will see what happens

 

[Jebiruph]

Update: I have spoken to my mechanic and Jeep wants to replace the entire PCB. I asked him to change the high amp bar next to the battery since it’s possible that the N3 or N4 fuses could be blown. So we will see what happens

There's probably nothing attached to N4, that's what makes it an option to move the N3 cable to.

 

[Tiger4Life]

Jeb do you think replacing the bar will fix it ?

 

[Tiger4Life]

There's probably nothing attached to N4, that's what makes it an option to move the N3 cable to.

Jeb do you think replacing the fuse bar will fix it ?

 

[Tiger4Life]

Jeb do you think replacing the fuse bar will fix it ?

There's probably nothing attached to N4, that's what makes it an option to move the N3 cable to.

My mechanic said they don’t want to do anything that isn’t stock. So moving the aux battery from N3 to N4 is not an option for them. He said I can do it but they won’t. He is going to replace the fuse bus bar today and we’ll see what happens. After that I’m out of options!

 

[Jebiruph]

Jeb do you think replacing the bar will fix it ?

As you describe the problem, I think it's likely. But temporarily moving the cable will test and verify. Using a temporary jumper to get 12v to the N3 terminal will also verify if it's a blown N3 fuse. If the main battery is charged, not seeing 12v at N3 also verifires.

 

[Tiger4Life]

Ok update:

they are going to change the fuse bus. Get it cracked and running then they are going to call and I’m going to go pick it up. I’ll see about moving the cable from n3 to n4. And disconnecting the aux batter all together. My mechanic said he could do that but was afraid it would shut down the dash and other things. Wish me luck

 

[Jebiruph]

Ok update:

they are going to change the fuse bus. Get it cracked and running then they are going to call and I’m going to go pick it up. I’ll see about moving the cable from n3 to n4. And disconnecting the aux batter all together. My mechanic said he could do that but was afraid it would shut down the dash and other things. Wish me luck

If they change the fuse bus, there is no need to move the cable. Moving the cable is a temporary work around until the fuse bus can get changed.

 

[Tiger4Life]

If they change the fuse bus, there is no need to move the cable. Moving the cable is a temporary work around until the fuse bus can get changed.

Thanks so much Jeb

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