12 volt system not working

[Texas 250]

I have a 2015 34 RESA, unplugged from main power and 12 volt system did not work, hydraulic jacks, slides and refrigerator would all work when unplugged from main power but all lights, water pump and awnings would not work, when I plugged back up to main power or ran generator all lights, water pump works, replaced 6volts battery last week due to age, had no issues after replacing, any ideas on what is going on. Thanks

[CaptainPalapa]

My first thought is similar to an old issue I had. 3 of our 4 lithium batteries had gone bad, in that if you wiggled the posts with a voltmeter the voltage would disappear and reapper. We had the same symptoms as you. Plugged in, things work (mostly) fine. Unplugged, and relying only on the batteries, no dice.

I would say unplug, then test those batteries again. If they are reading poorly, my thought is that your batteries aren't holding a charge or your charger/converter isn't doing it's job right. When you're plugged in, you're getting conversion from AC to DC, and into the 12v system, but not necessarily into the batteries.

[sourdo]

go through all your electrical connections, AND DON'T FORGET THE GROUNDS!!!

Make sure all is tight, you can get voltage, but when you command amps, nothing may happen. Before you go spending a ton of money on batteries, recheck everything.

And don't forget about fuses and circuit breakers.