What’s this red light for?

[NathanG]

So I’m having problems with my ESS battery. I was running my onboard air compressor without the engine on and all of a sudden my wrangler won’t start. I was running it for a total of 30 seconds I’m not sure what is going on. I had to jumpstart it after running compressor and it worked OK but after running it for 15 minutes I shut it off again, and it wouldn’t restart. Jump starting it works for now. Corresponding with this is this little red light on on the tachometer and I can’t find it anywhere in the maintenance manual what it’s for. Anyone have any idea?

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[WranglerAz]

That is the "Oh Shit" light. Seriously, I looked around as well and could not find what it was for.

 

[Redjl20737]

Is it the security alarm

 

[TheChucklesStart]

Have you tried using your key fob (the key side) to push the start button? It might be that your security alarm has decided that the car might be in danger of being stolen.

 

[Rhinebeck01]

@NathanG

I'm curious how your onboard compressor system is wired. Did you wire it directly to Pos on the JL's battery?

That is the red light for the Sentry key immobilizer system. Most people know this red light as they see it blinking constantly after they press the lock button on the fob. Lock the vehicle and the light starts blinking. It is really apparent .... very visible at night.

Since that vehicle security light is on during normal vehicle operation, and it has been running more then 10 seconds, it indicates that there is a fault in the electronics.

Normally, after pressing the ignition button to the Run position, the vehicle security light will turn on for three seconds for a bulb check. If the light remains on after the bulb check, it indicates that there is a problem with the electronics.

To get you past this issue... and this is if the compressor is wired in a fashion that does not cause issues..

Important: Your jump starting is not at all sufficient to get both the main and ESS batteries charged properly and sufficient enough where the JL will keep running and not shut itself off.

What you will want to do, is to trickle charge the JL for say 18 hrs.....by doing this you can be assured both the main and ESS batteries are fully charged.

Note: If the red sentry key security light stays on steady.... will not go out..... What you want to try ... to do.... is to totally disconnect all 12v power going to the JL. Killing 12v power to the JL, should reset the sentry key immobilizer system. Leave the power totally disconnected for a few minutes and then restore the 12v power. IF it resets and if you have no wiring / electronics issues, the light will go back on for 5 seconds and then go off. If it doesn't reset you will be heading to the dealership service dept..

Read here on how to kill ALL 12v power to your JL:

https://www.jlwranglerforums.com/forum/threads/to-kill-12v-power-to-the-jl-jlu.6244/

 

[NathanG]

Wow this is great info! I have the compressor wired to the 40 amp aux switch #1. The light was staying on after jump starting.

 

[Rhinebeck01]

Wow this is great info! I have the compressor wired to the 40 amp aux switch #1. The light was staying on after jump starting.

@NathanG

Nat, just try leaving the JL be and trickle charging it for say 18 hrs.. Attach trickle charger, pos cable to to main battery terminal and the charger's neg cable to a ground point. Let it charge. Will take that much time for the trickle charger to signal you the 2 batteries (Main and Aux) are fully charged. IF it takes less then 18 hrs. (it may take less time) then great.

After the charging, start the JL.... If that red sentry light goes out in 5 seconds and does not stay on, you have no more to do. IF by chance the red light stays on, try the 12v power kill I told you about.

 

[NathanG]

Last night I let it idle for approximately 45 minutes. This Morning it doesn’t want to turn over. It detects the key it seems. I’m pretty convinced the Ess. Battery is not taking a charge.

Of course this is all happening over Labor Day weekend 400 miles from home!

 

[Rhinebeck01]

@NathanG

It takes HOURS for the charging. You are not going to jump it. Get it on a trickle charger. The charge will make it's way to the ESS battery.

The JL's alternator is not going to get the batteries properly charged in any short order. So, your running the JL for 45 min. was pointless.

Stop fooling with it before you cause more issues.. 8-) Get it on a trickle charger and go out in another vehicle and enjoy the day.

 

[IPvFletch]

Wait so if my JL "battery dies", say from leaving my headlights on too long, and I need a jump, you're saying I'm still screwed if I shut the car off after a while, unless I let the car idle for like 24h to fully charge the batteries, or else use a trickle charger to charge it overnight??

 

[Rhinebeck01]

Wait so if my JL "battery dies", say from leaving my headlights on too long, and I need a jump, you're saying I'm still screwed if I shut the car off after a while, unless I let the car idle for like 24h to fully charge the batteries, or else use a trickle charger to charge it overnight??

Well, in regard to your stock headlights and stock interior lights, etc. the JL will turn those off for you, so no depleted battery if you leave the lights on.

Now, if you you wire up a reefer, compressor or such and it runs down the battery(s) then you can expect some, lets call them headaches.

The JL for one, is known to be real cantankerous if the batteriey(s) get depleted beyond a point where the JL is unhappy with same. And, jump starting is not going to be a fix... With that said, deplete the battery(s) and yup, you will have a dilemma.

A vehicle's alternator can't really be expected to bring up a really depleted battery. Sure, over time it may but ....

Anyway, if you deplete a battery(s) you should be hooking up a trickle charger to the vehicle. If you don't bring the charge up properly,.. fully, you may very well face... you undoubtedly will, face another depleted battery issue in the upcoming days. You can't expect and be 100% sure the alternator is going to get the depleted battery fully charged in a short time frame.

Trickle chargers can be had for less then $10 at Harbor Freight, etc..

Did you know.... Many lil or ladies that start their vehicle multiple times a day but then only drive a couple of miles, say to the grocery store, the post office, drug store and home are often plagued with battery depletion and no start situations. Battery gets run down by frequent starts and the alternator never gets the time to even bring up very minimal battery depletion because she does not drive the vehicle far and long enough. So, a month or so of grocery trips only and her vehicle will not start. YUP, grandma should be leaving her vehicle attached to a battery tender when it sits in the garage.

.

 

[NathanG]

Th Ess system is designed to work in stop and go traffic. How could it take so long to charge it? I do not have access to a trickle charge at the moment. I don’t think running a compressor discharged it since it was hooked to the main battery and it is fine. but maybe trying to start the car with the compressor running fried a relay...

In other news I can jump start it by hooking the jump pack to ground and terminal N1 on the fuse block. It’s starting right up like it has a charged battery. Trying to jump it per the manual ( red terminal and ground) didn’t work. This is good to know if you are in a Offroad situation and this happens after say using a winch.

I’d like to know what relay controls the ess to carry a spare if this happens again. I tried swapping a few in the fuse box but no dice.

 

[Rhinebeck01]

@NathanG

You are thick headed... that is for sure.... Trickle charge it and then decide what is wrong if anything...
Sure, you may have blown a fuse but ..

For ESS fuse, ....it is on OEM part number, 68368853AA which is a high amp fuse array that goes in the PDC. I believe ESS is pole N2 on the array.

 

[Rhinebeck01]

Back to the red light: I was working on my JLUR today and went to start it with the key fob sitting on the bumper. It started to turn over, then stopped and that red light came on. It stayed on(red light) and wouldn't start until I used the fob to start; like you would if the fobs battery was depleted.

@fdisker2000

Do you think that this is abnormal behavior? I would expect that, or similar behavior.

 

[NathanG]

Apologies for the density of my fore head that ess fuse is between the starter and the battery? Where can we get a copy of the diagram? I troubleshoot and repair helicopters for the govment but without a diagram it is pretty tough.

Thank you for your help btw.

Jumping it using terminal n1 works reliably and is how I am going to make the 8 hour drive to Tucson from LA. The local dealer was zero help over Labor Day weekend.

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