Both the Battery and the output of the converter/charger which is run by shore power connects to the 12VDC Distribution Panel.
Since yours work fine when on shore power and not when off the power grid it is saying your battery cables are not connected.
First thing you did to look for is to make sure your battery cables are connected properly to the battery terminals... Might just be a loose conenction at the terminals...
Then find the word "NEG" or the symbol "-" printed on the battery case and make sure this is the battery cable that goes to the trailer FRAME GROUND. Hand trace this out to be sure. If this is correct then look for a IN-LINE FUSE (may also be a circuit breaker) close to the battery terminals and make sure this fuse (or breaker) is OK.
The next thing to check is two FUSES on the 12VDC Distribution Panel labeled "REVERSE POLARITY". These will be located off to themself on the panel. Don't replace these fuses if they are blown until you correct the battery cables to their correct position on the battery terinals. Otherwise it will just blow the fuse again if it is incorrectly terminated.
Some installs may have a BATTERY DISCONNECT Switch installed. This will need to be "ON" as well...
If all the above is correct then you should have 12VDC coming from your battery at the BATTERY connection on the 12VDC Distribution Panel...
A MULTIMETER ($7-$15 LOWES/WALMART/Auto Parts stores) is a great thing to have for checking these DC VOLTAGES and to determine where the connection may be opened...
Let us know what you find...
Roy Ken
My Posts are IMHO based on my experiences - Words in CAPS does not mean I am shouting
Roy - Carolyn
RETIRED DOAF/DON/DOD/CONTR RADIO TECH (42yrs)
K9PHT (Since 1957) 146.52M
2010 F150, 5.4,3:73 Gears,SCab
2008 Starcraft 14RT EU2000i GEN
2005 Flagstaff 8528RESS