ESS Battery Cable Caution and ESS (N3) Fuse Warning

[FlabbyCouch]

After seeing this post, https://www.jlwranglerforums.com/forum/threads/help-with-n-terminal-connections.74322/ , I looked at what happens if the N3 cable gets connected to N4 instead.

Since both the N3 and N4 fuses supply system power through a 150A fuse, it will not make any difference if the aux battery cable gets connected to N4 instead of N3.

This means that if you get stranded due to a blown N3 fuse isolating the aux battery and system electronics, you can move the aux battery cable from the blown N3 terminal to the good N4 terminal to restore system power to the aux battery and system electronics. If there's already a cable connected to N4, it is providing power to your auxiliary switches. Be aware you will lose power to the auxiliary switches when you remove the existing N4 cable to relocate the N3 cable to the N4 terminal.

You really saved my butt from a massive headache. Was wiring a light bar and didn’t know what could’ve happened when nearly everything in the Jeep stopped working. Put N3 on N4 and the Jeep is running fine now until the new fuse assembly arrives. A couple questions… for anyone in the group that can answer them:

1. How can I tell which radiator fan I have so I can order the right fuse assembly?
2. Does N3 have to do with the backup camera also? Realized I lost the backup camera after I got everything up and running. Or do I have to take it to the dealer once I replace the fuse assembly and have them reflash? I have a ‘21 Gladiator Mojave so I’m pretty sure it’s the 100A one, but I want to be 100% sure. TIA

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[Bob Burd]

Note that the terminals are keyed to make this difficult. You can force it however...

 

[superdude]

After seeing this post, https://www.jlwranglerforums.com/forum/threads/help-with-n-terminal-connections.74322/ , I looked at what happens if the N3 cable gets connected to N4 instead.

Since both the N3 and N4 fuses supply system power through a 150A fuse, it will not make any difference if the aux battery cable gets connected to N4 instead of N3.

This means that if you get stranded due to a blown N3 fuse isolating the aux battery and system electronics, you can move the aux battery cable from the blown N3 terminal to the good N4 terminal to restore system power to the aux battery and system electronics. If there's already a cable connected to N4, it is providing power to your auxiliary switches. Be aware you will lose power to the auxiliary switches when you remove the existing N4 cable to relocate the N3 cable to the N4 terminal.

This problem seems to be occurring more often. The JL/JT won't start (hot or cold) and the system electronics are going crazy. Jumpstarting doesn't work and the tow to the dealer results in a new aux battery. A few days later the same thing happens again, won't start, flashing electronics, towed to the dealer who finds and replaces another bad aux battery. This cycle continues until the dealer finds an replaces the bad high capacity fuse array with the blown N3 fuse.

Here's how the N3 fuse gets blown. I've modified my battery cable diagram to show the battery cables disconnect from the main battery. You can see that when the negative cables are disconnected from the main battery, the aux battery negative cable is still connected to ground. When the positive cable is removed from the main battery, the aux battery positive is still connected to it. At this point, it will look like battery power is completely disconnected, but if the positive cable is allowed to contact ground, it will create a short circuit from ground to the aux battery positive terminal and blow the high capacity N3 fuse.

There is not an immediate impact when the N3 fuse blows, but the aux battery and system electronics are now isolated from the alternator and the main battery. Everything will work as normal until the aux battery no longer has enough charge left to power up the electronics, resulting in the flashing system electronics and an inoperative jeep.

With the system electronics and the aux battery isolated from the main battery, connecting a charger to or trying to jump start from the main battery does not help, you need to get power to the N1 terminal. This can be done by using a jumper from the main battery positive to N1, but the aux battery ground cable needs to be completely disconnected from ground first. Otherwise the depleted aux battery will be trying to charge through the jumper, taking power from the system electronics and possibly exceeding the capacity of the jumper wire used. A fused bypass jumper (https://www.jlwranglerforums.com/forum/threads/3-6l-ess-aux-battery-bypass.17293/post-423590) can be used, but this application may exceed the capacity of a 30A fuse.

Edit - To make sure the aux battery is completely disconnected, disconnect both negative cables like this.

Edit - If the N3 fuse (or any of the high capacity fuses) is blown, the whole fuse array has to be replaced. There are 2 different fuse arrays to accommodate the 2 different radiator fans.

fuse array with 60A fan - 68368853AA
fuse array with 100A fan - 68368854AA

I'm so greatful for this information. I may be the next person you saved from spending unnecessary $ at the dealership. My battery is currently (hah...) drained, though prior to draining, it would start without issue, flicker, then die. If my N3 fuse is blown, which I believe to be the case, and I switch the wire over to the N4 terminal, do you know if I'll be able to recharge the battery to an operational level from that point?

 

[Du0377]

This problem seems to be occurring more often. The JL/JT won't start (hot or cold) and the system electronics are going crazy. Jumpstarting doesn't work and the tow to the dealer results in a new aux battery. A few days later the same thing happens again, won't start, flashing electronics, towed to the dealer who finds and replaces another bad aux battery. This cycle continues until the dealer finds an replaces the bad high capacity fuse array with the blown N3 fuse.

Here's how the N3 fuse gets blown. I've modified my battery cable diagram to show the battery cables disconnect from the main battery. You can see that when the negative cables are disconnected from the main battery, the aux battery negative cable is still connected to ground. When the positive cable is removed from the main battery, the aux battery positive is still connected to it. At this point, it will look like battery power is completely disconnected, but if the positive cable is allowed to contact ground, it will create a short circuit from ground to the aux battery positive terminal and blow the high capacity N3 fuse.

There is not an immediate impact when the N3 fuse blows, but the aux battery and system electronics are now isolated from the alternator and the main battery. Everything will work as normal until the aux battery no longer has enough charge left to power up the electronics, resulting in the flashing system electronics and an inoperative jeep.

With the system electronics and the aux battery isolated from the main battery, connecting a charger to or trying to jump start from the main battery does not help, you need to get power to the N1 terminal. This can be done by using a jumper from the main battery positive to N1, but the aux battery ground cable needs to be completely disconnected from ground first. Otherwise the depleted aux battery will be trying to charge through the jumper, taking power from the system electronics and possibly exceeding the capacity of the jumper wire used. A fused bypass jumper (https://www.jlwranglerforums.com/forum/threads/3-6l-ess-aux-battery-bypass.17293/post-423590) can be used, but this application may exceed the capacity of a 30A fuse.

Edit - To make sure the aux battery is completely disconnected, disconnect both negative cables like this.

Edit - If the N3 fuse (or any of the high capacity fuses) is blown, the whole fuse array has to be replaced. There are 2 different fuse arrays to accommodate the 2 different radiator fans.

fuse array with 60A fan - 68368853AA
fuse array with 100A fan - 68368854AA

Hey there,
So the same exact thing happened to me yesterday, everything went haywire and the. Wouldn’t start. I did what most people with limited knowledge do and pulled the batteries and replaced them. Started up but then did the same thing. Researched thinking it is the pcm but now i think its the fuse array. I pulled it and headed to the dealership to pick up a new one and installing it later today. Fingers crossed, I hope it works.

 

[JLR_AEV]

Hey there,
So the same exact thing happened to me yesterday, everything went haywire and the. Wouldn’t start. I did what most people with limited knowledge do and pulled the batteries and replaced them. Started up but then did the same thing. Researched thinking it is the pcm but now i think its the fuse array. I pulled it and headed to the dealership to pick up a new one and installing it later today. Fingers crossed, I hope it works.

Keep us posted

 

[SPARTANJT]

You really saved my butt from a massive headache. Was wiring a light bar and didn’t know what could’ve happened when nearly everything in the Jeep stopped working. Put N3 on N4 and the Jeep is running fine now until the new fuse assembly arrives. A couple questions… for anyone in the group that can answer them:

1. How can I tell which radiator fan I have so I can order the right fuse assembly?
2. Does N3 have to do with the backup camera also? Realized I lost the backup camera after I got everything up and running. Or do I have to take it to the dealer once I replace the fuse assembly and have them reflash? I have a ‘21 Gladiator Mojave so I’m pretty sure it’s the 100A one, but I want to be 100% sure. TIA

I just had the same problem and same question. Easiest way to tell what fuse array you have is by removing the fuse and locating the part number. 68368854AA has the 100A fuse.

HOWEVER, if your in a position where you can't remove the fuse array you can stick your phone's camera down where the cooling fan is located (obviously, while its not running!) and snap a picture of the part number. There will be two stickers but you should be looking for a part number that looks like this

...55AD is the cooling fan for the 100A fuse that comes with the tow package.

...99AD is for stock cooling fans and is a 60A fuse

Hope this helps.

You really saved my butt from a massive headache. Was wiring a light bar and didn’t know what could’ve happened when nearly everything in the Jeep stopped working. Put N3 on N4 and the Jeep is running fine now until the new fuse assembly arrives. A couple questions… for anyone in the group that can answer them:

1. How can I tell which radiator fan I have so I can order the right fuse assembly?
2. Does N3 have to do with the backup camera also? Realized I lost the backup camera after I got everything up and running. Or do I have to take it to the dealer once I replace the fuse assembly and have them reflash? I have a ‘21 Gladiator Mojave so I’m pretty sure it’s the 100A one, but I want to be 100% sure. TIA

 

[ells]

First a huge thanks to @Jebiruph You saved another Jeeper a lot of time and money.

My experienced with 2018 JL Wrangler Sport, 3.6L engine, with 37k miles:

• Out running an errand, went inside some place for 5 min
• Came back out, tried to start, engine wouldn't crank
• Electric was working fine... headlights, radio, air, etc... confused me away from battery problem... only later realized it was all running off the aux battery
• Tried to jump using a Type S Jumpstarter that was not up to the task (maybe I got the wrong one?), but I didn't suspect battery because above, and ignorance, so thought it was relay or who knows what...
• Anyway, I thought I was stranded... but I have road side assistance through a warranty...
• Tow guy showed up, jumped successfully, but then...
• Tow guy said "I can check your alternator by disconnecting the positive on your battery while it's running"... Ignorant me, I thought, well yeah let's do a quick check...
• I think when he did that is when the N3 fuse blew. Engine was still running but when I got in to leave I saw the dreaded 'Stop Safely, System Will Automatically Shutoff' message, no power steering... wouldn't even go anywhere...
• Tried stop and another start but now electric started freaking out, wipers coming on, etc
• Towed! Damnit...
• That night, did some reading, including this post, learned some stuff about Jeep electrical
• Next day got into the lot where it was towed, swapped the main battery, no start! Damnit...
• Moved the N3 cable over to N4 on the fuse array... started no problem! Sweet.
• Got it home, unhooked everything, pulled the fuse array and tested with multimeter, confirmed N3 was indeed blown.
• Running on the N4 fuse now and ordering a couple fuse arrays, one to run and one for backup.

In addition to this post, I found this youtube video helpful for how to replace and how to confirm the blown fuse with a multimeter (around 3 min into the video)... did exactly this and got the same result



Do be aware that there are two different fuse arrays as mentioned in this forum thread. In the YT video above that guy has the 100A fuse for the radiator fan... mine was the 60A fuse model. Make sure you pull your specific fuse array out and check it before you order anything.

Problem solved! But leaving a (probably dumb) question for the community... would pulling the positive cable off the main battery, while running, be enough on it's own to blow the fuse? Or would it still have to touch some ground either way (engine running or not)?

 

[Bob Burd]

Pulling the + cable will not blow the fuse until it then touches ground.

 

[SadRobot]

How long can you run off of the N4 fuse? If my N3 is blown and I move it over to N4 can I drive it at least 165 miles to bring the Jeep back home?

 

[Jebiruph]

How long can you run off of the N4 fuse? If my N3 is blown and I move it over to N4 can I drive it at least 165 miles to bring the Jeep back home?

Indefinitely - until it gets blown. It's a 150 amp fuse just like N3, so it works the same.

 

[Pig-Pen]

Silly question but is this issue still a possibility if the auxiliary battery has already been bypassed? Im thinking yes since apparently there is always power present…… And what if the auxiliary has been completely deleted from the system? Would that be the smart thing to do? To avoid this potential issue?

 

[Badbear0416]

As I don't have the aux battery on etorque new rubicon how is it possible for a fuse array to go bad possibly after I just finished the hard top wiring kit as dealer forgot that option so I installed and bow no acc or start or windows Yet everything else seems to work ??? Ty

It was mentioned it could be the fuse array but I never once crossed pos and neg cables and no aux battery string install

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