2021 Wrangler - ESS Not Ready Unless AC / Heater is Completely OFF

[mgroeger]

Main battery connects to N2 which is a rail. It goes through a fuse to N3 which then goes to a power relay and then to the ESS battery. Unless you know the state of that relay to be open you will have the two batteries connected.

Also removing the negative cable from the main battery still keeps the ESS battery connected to the chassis. Don't know if that matters but that's the way it's wired.

So to avoid any confusion or possible masking of a problem the best way to test to is completely disconnect the batteries and load test them that way.

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[Gee-pah]

Main battery connects to N2 which is a rail. It goes through a fuse to N3 which then goes to a power relay and then to the ESS battery.

...yes...the ESS battery positive, which flows out the ESS battery negative, so to speak, and off to a bunch of dangle cables (as per my directions) that, as your point below, do connect to the body ground, a fair point as it relates to the ESS battery, but not the main battery so as to in any way complete a circuit with the main battery. No circuit means to me that the main battery being load tested this way is electrically equivalent to the main battery being tested with no cables on any terminal, with it 50' away from the vehicle on a countertop, say.

Unless you know the state of that relay to be open you will have the two batteries connected.

That relay is closed when the 3.6L JL it at rest. It opens for an instant at crank and during ESS events to separate the batteries. Whether it's open or closed state is immaterial as a full circuit does not make its way back to the main battery given that battery's untouched negative post: care of the dangling cables.

Also removing the negative cable from the main battery still keeps the ESS battery connected to the chassis. Don't know if that matters but that's the way it's wired.

Now this one is fair. It may not matter, but yes, appliances that may be on even with the JL is off can tap the ESS battery and affect its load test. For example, if someone had something plugged into the cargo area (if equipped) 12V plug, which by default from the factory is a battery outlet (always on) then yes, particularly if it drew considerable current---or if there was a vehicle wiring problem. Most other things in the rig aren't on when the rig is off or draw much current to make a difference---but yes, your isolation of the body ground from the negative cable leading away from the ESS battery has electrical merit.

So to avoid any confusion or possible masking of a problem the best way to test to is completely disconnect the batteries and load test them that way.

I don't disagree so much as I might find it overkill and extra work. Sure, wiring could get crossed and all, but if one post of a battery is untapped, that battery is isolated: current can not flow to or from it provided the battery itself has no internal shorting: in which case sitting it on a countertop 50' away won't address anyway.

 

[Hutchy68]

@Chupacabra came up with the right explanation.

Tested the AC on and temperature set at 71/72 with the fan on anything other than max. ESS showed ready and worked. Windows down, no AC and interior fan off, ESS works. No AC, interior fan on, ESS doesn't work just as you stated in your post.

So it is proven to me, the dealership mechanics and techs don't even understand the system. Jeep is stupid because no AC means less load, but no ESS. After all, you only have the blower fan on. So, AC is more load, the fan is still on, but ESS works. I know the compressor kicks out when ESS engages, so their logic is really flawed.

 

[J0E]

If the cabin isn't sufficiently heated or cooled to your set temperature, the ESS will not engage.

In the morning I drive with the blower on (no A/C) because it's reasonably cool outside. The ESS does not kick on under these conditions because the cabin will never cool down enough but I like the air blowing in. If I turn the HVAC system completely off, it will engage the next time I come to a stop.

That's almost exactly what I reported.

Console reports ESS not read cabin cooling or heating if drivers side temperate control is more than 2 degrees cooler than temperature on the console AND the AC OFF. If I'm stopped and raise the drivers side to within 2 degrees of the reported temperature, it reports Stop/Start Not Ready. If I then left off the brake and immediately touch the break, the message changes to ready and the engine shuts down.

I like ESS when I drive through town on my way to wheeling. But I hate to have to put the drivers side temperature at near 80 to get it working. I sometime engage my AC.

I don't understand this part

In the morning I drive with the blower on (no A/C) because it's reasonably cool outside. The ESS does not kick on under these conditions because the cabin will never cool down enough but I like the air blowing in. If I turn the HVAC system completely off, it will engage the next time I come to a stop.

On my 2021 JLR, you can't turn the fan completely off. You report in the morning AC off and ESS is not ready, but then you say

If I turn the HVAC system completely off, it will engage the next time I come to a stop.

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