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ESS Battery Cable Caution and ESS (N3) Fuse Warning

Jebiruph

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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.

Jeep Wrangler JL ESS Battery Cable Caution and ESS (N3) Fuse Warning main positive cable 2.PNG



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

Jeep Wrangler JL ESS Battery Cable Caution and ESS (N3) Fuse Warning main neg detail



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
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Htfan

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Great info! Appreciate the diagram. This is one of those topics that keeps coming up as new JL/JT owners join the forum.
 

drivingfool

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Does this happen to the stock config, or after someone pulls the battery for some reason?
 

SargeW

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Good info and diagram to file away for future use. Thanks
 
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Jebiruph

Jebiruph

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Does this happen to the stock config, or after someone pulls the battery for some reason?
This is based on the stock ESS system wiring of the batteries.
 

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Jebiruph

Jebiruph

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So never let the positive main touch ground, no matter what?
If your not sure it's completely disconnected, play it safe. Here's a picture I took with both cables disconnected from the main battery and the LED connected to the positive cable show's it still has power.
Jeep Wrangler JL ESS Battery Cable Caution and ESS (N3) Fuse Warning bmp pos led 3
 

RFR JLR 2.0

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Thanks for sharing this. Had my aux battery and fuse fall and replaced by the dealer. I need to study this more.
 
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Jebiruph

Jebiruph

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To make sure the aux battery is completely disconnected, you have to disconnect both negative cables. (I guess I should have posted this in the first post)

Jeep Wrangler JL ESS Battery Cable Caution and ESS (N3) Fuse Warning main neg detail
 

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Jebiruph

Jebiruph

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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
 
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Jebiruph

Jebiruph

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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.

Jeep Wrangler JL ESS Battery Cable Caution and ESS (N3) Fuse Warning pdc label 3


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.
 

Rhinebeck01

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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.

Jeep Wrangler JL ESS Battery Cable Caution and ESS (N3) Fuse Warning pdc label 3


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.
@Jebiruph

Great info...... we learn something every day..
 

A10Cajun

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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.

Jeep Wrangler JL ESS Battery Cable Caution and ESS (N3) Fuse Warning pdc label 3



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

Jeep Wrangler JL ESS Battery Cable Caution and ESS (N3) Fuse Warning pdc label 3



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
WOW! Again youā€™re fantastic information saved my bacon tonight! Iā€™ve been racking my head trying to figure out whatā€™s going on with my 2018 JL, I pulled off the N3 High capacity fuse array, and tested the N3 with an ommeter and found out that itā€™s blown. Now I know why my brand new aux battery DIED right in the middle of an intersection. Time for a jumper.
Jebiruph, I owe you at least a pint or morešŸ˜šŸ˜. Thank you so much, Danny Martin
 
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Jebiruph

Jebiruph

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WOW! Again youā€™re fantastic information saved my bacon tonight! Iā€™ve been racking my head trying to figure out whatā€™s going on with my 2018 JL, I pulled off the N3 High capacity fuse array, and tested the N3 with an ommeter and found out that itā€™s blown. Now I know why my brand new aux battery DIED right in the middle of an intersection. Time for a jumper.
Jebiruph, I owe you at least a pint or morešŸ˜šŸ˜. Thank you so much, Danny Martin
As I mentioned in post #12, you should be able to pull the cable of off N3 and move it to N4 to bypass the blown N3 fuse until it gets replaced.
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