Issues after replacing both batteries.

[The Last Cowboy]

I just replaced my main and aux batteries. They were 3 years and 4 months old. For over a year I have been operating with no issues with a message that stated that ESS was not available due to the battery charging. In the time that I have been operating in that mode, there have been to incidences of a slow crank, then 4 days ago a no start. The Jeep sat unsold on the dealer lot for nearly 6 months when I bought in in May of 2020, at the height of the Covid scare.

So, not wanting to make a trip to town for a possible warranty replacement of one ot both batteries, I decided to just buy better ones. I bought Super Start Platinum replacements the main is a larger H7 94R and the aux is a 14. I've been working on cars since I was a teen and have replaced countless batteries without issue. I got my multimeter out and the main was low 11s and the aux was below 11. The volt reading on the dash has been mostly 14.3 since it was new. There were no electrical glitches or anomalies with the original batteries, other than what I described above.

I charged both batties to 100% prior to install,as I always do. Then I installed both, going from the top for the aux (which I didn't find difficult) and encountered no issues. It started quickly and there was a new ESS message that I had not seen before, an A! light and a service ESS message. I drove it for about 20 miles hoping that the sytem would reset. I now noticed that the volt reading was showing that the sytem is now charging at 14.5 volts. As i was driving, I noticed that my feet were cold. I went to turn on the heat and found that the entire HVAC cluster is not functioning.

I checked all of the fuses, disconneted/reconnected the IBS. I pulled the HVAC relay and swapped it with the fuel pump relay. No difference, I even swapped the H2-H7 fuse array with no changes. I pulled the F42 and disconncted the aux gound. The ESS warning light and message did not go away. After letting it sit overnight, I disconnected all of the grounds then reconnected them. No changes other than the volt reading is now in the low 13s at idle. I'm thinking the ESS light and waring may be due to the HVAC clusted being out, as the EES switch is located on it. I have the base HVAC.

Any thoughts on what else I can try would be appreciated. I really don't want to go to the dealer for what should be a simple issue.

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[entropy]

So your main was at 11Volts when new? Aux below 11... Go get warranty replacements... That is not good. And should have never installed those batteries. Batteries sitting with those voltages would get damaged very quickly.

I am even surprised you were able to charge those batteries. My guess is one of them is severely damaged and giving you the electrical issues. It is difficult to troubleshoot issues with the JL batteries when running that stupid dual battery setup. Which is why I ended bypassing the aux.

I had the same issue you had. Jeep sat in the dealer for 6 months. Had the same message. Turned out my jeep was running on the aux battery and the main was super weak lol.

New batteries fixed it. But they both read 12.6volts before I installed.them which means they were store properly and kept charged.