What's the meaning of this?

[Gruffid]

Nope - bad info. It's not always how it works. In fact, the aux battery can be fine and the main battery go bad.
The aux switches kick out at about 11.8 volts. Below that they shut down.
That bit about "the aux battery always goes taking out the main battery" just isn't the case in every case. Happens sometimes, but for sure not always.
It could be that because it's COLD out, he's not driving it OFTEN enough or FAR enough to keep COLD batteries up.

But throwing mud at the wall to see what sticks won't help with a true solution.
Best to charge them properly, correctly, and have them tested, or measure the voltage of each, etc.

This is tongue-in-cheek:

What do you mean this is bad info?!? Clearly the starter battery is low! How could I possibly have bad info? I have the best info the world has ever seen!

And the term “probably” indicates a 55-80% confidence that what I said is assessed to be true! And I make the best assessments - ever!

?

back to seriousness SP, I appreciate your thoroughness and defer to your experience.

That said, the two similar events as described above that I’ve had (first with my wife’s Wrangler, second with my Gladiator), the root cause was that the failing aux battery killed the starter battery, eventually resulting in both vehicles needing to be jump-started before we took them to the dealer for assessment. The dealer replaced the batteries under warranty.

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[ShadowsPapa]

This is tongue-in-cheek:

What do you mean this is bad info?!? Clearly the starter battery is low! How could I possibly have bad info? I have the best info the world has ever seen!

And the term “probably” indicates a 55-80% confidence that what I said is assessed to be true! And I make the best assessments - ever!

?

back to seriousness SP, I appreciate your thoroughness and defer to your experience.

That said, the two similar events as described above that I’ve had (first with my wife’s Wrangler, second with my Gladiator), the root cause was that the failing aux battery killed the starter battery, eventually resulting in both vehicles needing to be jump-started before we took them to the dealer for assessment. The dealer replaced the batteries under warranty.

I hope his crank battery wasn't down to 11.8 volts............

Aux Switch Bank Module (ASBM) Minimum Voltage Time: 10 sec
Aux Switch Bank Module (ASBM) Battery Minimum Voltage: 11.8 V

In any case - I'm suspecting most would agree - he needs to do some simple, basic testing that can be done with the truck's cluster volt meter and/or a $15 meter from Walmart or Menards. (and buy a decent battery charger for AGM batteries)
And move to a warmer climate........... (that's my wife's suggestion)

 

[Rusty PW]

I hope his crank battery wasn't down to 11.8 volts............

Aux Switch Bank Module (ASBM) Minimum Voltage Time: 10 sec
Aux Switch Bank Module (ASBM) Battery Minimum Voltage: 11.8 V

In any case - I'm suspecting most would agree - he needs to do some simple, basic testing that can be done with the truck's cluster volt meter and/or a $15 meter from Walmart or Menards. (and buy a decent battery charger for AGM batteries)

And move to a warmer climate........... (that's my wife's suggestion)

.......and have frozen iguanas fall on you. Dropping out of the trees.

 

[ShadowsPapa]

.......and have frozen iguanas fall on you. Dropping out of the trees.

Funny you mention that now - my wife was just talking about "what if" we moved closer to my son and his family - we'd have some other reason to wear hats.

 

[wv_gladiator]

I think the better question is… How are you averaging 20.8 mpg? ? ?

Diesel

 

[ShadowsPapa]

Weird how my brain works - when I first saw the subject, I immediately thought of the Monty Python film.

 

[Hawkeyes3312]

I had the same message for about the last 3 months, even prior to the cold that we're stuck with in Iowa until April. Anyway, I found a coupon on the Mopar site for my dealer for a free battery charging system test. It claimed it was a value of $139.99. I had the test run and it confirmed the auxiliary battery was failing. I just had it replaced on Wednesday prior to winter storm Elliot's arrival. I went with the Mopar replacement as it has a 3 year warranty as opposed to aftermarket which only carries 1 year. As well, they charged me 1 hour of labor to complete the install so not too bad.

 

[ShadowsPapa]

I found a coupon on the Mopar site for my dealer for a free battery charging system test. It claimed it was a value of $139.99.

If you have seen the process involved with testing batteries - no surprise they value it at that. They must use very specific equipment and follow a laminated check list of things down the line, especially for warranty. For warranty, they literally must have their battery tester on their WiFi so it can transmit the results to Jeep. If the battery voltage is below a certain point, they have to use a specified charger to reach a certain voltage and state of charge before they can test the batteries.

If battery voltage is low (and the PCM does a quick check of the aux battery by itself when you push that big button to start the truck) and it's below 11.8volts, the aux switches won't work.

 

[Hoss]

Subscribing because I am having the same issue with my diesel…. Less than 14k miles, and I’ve had the Jeep for about 14 months. ESS stopped working a few months back, before the cold weather moved in, and I have had a few startups lately where I have gotten the message about the aux switches.

I planned on taking the vehicle to the dealership to have it looked at, and inquire about the HPFP recall. I guess that I need to get a move on to the dealership before it leaves me stranded..

 

[keithcroshaw]

Sorry, but the dude could be right, here.

The truck can start on pretty low batteries, however, the aux switches have a minimum voltage cut-off below which they won't operate.





Do this - next time you start your truck, keep your foot OFF the brake pedal, press the start button two times. Now scroll the cluster up or down to get to the display that shows oil temp, engine temp and so on and scroll left or right to see the voltage.
Read it while the truck is NOT running.
Now start the truck normally and check the voltage as it's running.

Batteries are harder than heck to charge when it's cold outside. And if your truck sits a lot - it may be your batteries are ok, but you don't drive it OFTEN enough or FAR enough.

The issue could actually be the main battery OR the aux battery. That's why it's best to check voltage with it not running, at rest, and see where the voltage is with it running.
The diesel likely, though, is a bigger load on the starter so a battery at 11.8 isn't going to crank it well in cold weather - making the aux more likely.

Bottom line - time to charge the batteries fully with a good charger and have them load tested.

I’ve been worried about this, mines been mothballed lately.

 

[ShadowsPapa]

I’ve been worried about this, mines been mothballed lately.

Seriously, do get a decent battery charger or tender, and if your truck sits more than 2 or 3 days, especially over a week, keep the batteries up. You can connect to the top of the main or crank battery and it will keep both up without disconnecting things.

 

[keithcroshaw]

So I want to build it up to be an overpriced camping rig, I mean overlanding rig but I’m not keen on dual batteries. I think I want to mount one of those Noco shore power receptacles that I can split, one to charge my all in one battery in the bed and one to charge my starter. I’ve never run anything from in the bed to the engine bay but I imagine it’s doable for a novice. I also want those oracle aux lights that replace the reflectors so I should run all the 12V together for that. Keep the actual battery charger in the bed to limit 120V wiring to that one point where it comes in.

 

[firemedic2714]

I got that message along with ESS offline. It was a bad primary battery.

 

[Lunentucker]

So I want to build it up to be an overpriced camping rig, I mean overlanding rig but I’m not keen on dual batteries. I think I want to mount one of those Noco shore power receptacles that I can split, one to charge my all in one battery in the bed and one to charge my starter. I’ve never run anything from in the bed to the engine bay but I imagine it’s doable for a novice. I also want those oracle aux lights that replace the reflectors so I should run all the 12V together for that. Keep the actual battery charger in the bed to limit 120V wiring to that one point where it comes in.

You sound like a candidate for the Genesis dual battery system.

 

[Jeepasaurus_Rex]

Yeah, that's pretty bad for a diesel.

Yea, I wonder if there is another issue here too. Should be way more than 20.8!

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