You have 2 electrical systems---120V AC and a 12V DC
Shore power (or generator) provides the 120V AC power via the power cord.
You have an AC Power panel with Circuit Breakers (Main breaker--30A and then individual 20/15A breakers) Individual ones feed---A/C Unit, water heater electric element if it has one & outlets.
The 'Converter' is feed from the 120V AC system....either via circuit breaker or plugged into an outlet.
With 120V AC power supplied the converter will provide the 12V DC power and recharge/maintain charge on trailer battery.
W/O 120V AC power the trailer battery will supply the 12V DC system
Need to find/open AC Power Panel and check all circuit breakers (turn them OFF then back ON)
DC Dist System is typically part of that AC Panel........converter is behind.
It has to have AC Power to provide 12V DC. If it is working you can measure 13.2V DC on battery cables were they are connected in DC Dist. Section.
If less than 13.2V DC then converter is not functioning properly.
New battery.......make sure it is connected correctly and not reversed.
Trace which cable goes to trailer frame...that is Negative cable. Colors of cable don't always make sense. If connected backwards you can blow the 'reverse polarity' fuses (30a or bigger) on the converter
AS stated.
You need good 12V DC to operate Water Heater propane (and electrical on Atwoods), Furnace, Fridge, Thermostat for A/C, lights, water pump, ceiling/exhaust fans etc.
