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Dead JK after being parked for a few weeks


Kaptain Karnage

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So, my son's 2 door Rubi has been parked (admittedly outside in damn cold weather) at school for ~3 weeks while he was home for the holidays. He got back yesterday, and this morning when he tried to start the Jeep it was stone dead. No lights coming on at all when turning on the ignition, nada.

Got him to disconnect the battery, check voltage, and it was down to ~8v. He tried jump starting from another vehicle, but even when connected up, no electrics at all. He went and got a replacement battery, fitted it, just on the off chance that the battery itself had some physical issue, and still no joy.

So right now I'm thinking it has to be some kind of fuse that's gone, if there is no voltage getting anywhere? Any suggestions on what to check first? Any help would be deeply appreciated. Next step seems to be to check whether the fuse box is getting power at all: he'll go do that once he's defrosted himself from the battery swapping work.
 

BLACKJKU

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Did he clean the battery clamps and inspect them closely for corrosion? What year is the JK?
 
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Kaptain Karnage

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Did he clean the battery clamps and inspect them closely for corrosion? What year is the JK?
Yeah, battery clamps are still in perfect condition. Not yet sure about the condition of the connector in the fuse box, but he'll check that next, once he's warmed up a bit. It's a 2015 2 door Rubi. Forgot to mention he has the Genesis Offroad dual battery system installed.
 

Vman

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Yeah, battery clamps are still in perfect condition. Not yet sure about the condition of the connector in the fuse box, but he'll check that next, once he's warmed up a bit. It's a 2015 2 door Rubi. Forgot to mention he has the Genesis Offroad dual battery system installed.

Does he have two batteries installed?

If so, you have the main cranking battery and the booster battery. If the main battery is bad there's a button you can use to jump start it from the booster battery. If the booster battery goes bad the isolator is supposed to separate the two to prevent the draining of the cranking battery.

If the cranking battery went bad and can't be charged by the booster that might explain it. Did he disconnect the system and check both batteries?

Genesis has a really good site that explains what to test, how to jump start it, how to test it, etc. Let me see if I can find a link.

Here it is:

 
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Kaptain Karnage

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Does he have two batteries installed?

If so, you have the main cranking battery and the booster battery. If the main battery is bad there's a button you can use to jump start it from the booster battery. If the booster battery goes bad the isolator is supposed to separate the two to prevent the draining of the cranking battery.

If the cranking battery went bad and can't be charged by the booster that might explain it. Did he disconnect the system and check both batteries?

Genesis has a really good site that explains what to test, how to jump start it, how to test it, etc. Let me see if I can find a link.

Here it is:

Yeah, Genesis system with both batteries installed. He even swapped out the cranking battery for a new one, as the original one was showing only 8 volts on an open circuit. Even with the new battery at 12V, I got him to check the voltage coming into the fusebox, and that was only showing 4V, which is obviously not right. The trouble is that the Jeep was parked outside, and it was -15F before windchill, which was making it impossible to do further work.

We've had it towed to a local mechanic shop who have a good reputation. At least they'll be able to work on it in a warm enclosed space. I'm speculating that it's a connector somewhere between battery and fusebox that has gone brittle with the cold or something like that, but they're taking a look tomorrow, so we'll find out soon enough.
 
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BLACKJKU

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Yeah, Genesis system with both batteries installed. He even swapped out the cranking battery for a new one, as the original one was showing only 8 volts on an open circuit. Even with the new battery at 12V, I got him to check the voltage coming into the fusebox, and that was only showing 4V, which is obviously not right. The trouble is that the Jeep was parked outside, and it was -15F before windchill, which was making it impossible to do further work.

We've had it towed to a local mechanic shop who have a good reputation. At least they'll be able to work on it in a warm enclosed space. I'm speculating that it's a connector somewhere between battery and fusebox that has gone brittle with the cold or something like that, but they're taking a look tomorrow, so we'll find out soon enough.

Thanks for the update, be sure to let us known the outcome.