Your 12VDC Distribution Panels provides POWER to your 12VDC items.
Both the CONVERTER/CHARGE and the trailer battery setup connect to this Distribution Panel (Where all your 12VDC FUSES are located) to operate all of the 12VDC items.
You will need to start at the battery terminals and measure your 12VDC there first. If the battery is fully charged this will read 12.6=7VDC at the battery terminals without the shore power turned on.
If all was normal you would see 13,6VDC or more at the battery terminals depending what the charge state of the converter/charger unit is when you connect up to the shore power.
With shore power turned OFF I would start at the battery terminals and measure the 12.6-7VDC first. Then I would go to the heavy wire terminals on the 12VDC Distribution Panel and you should read the same 12.6-7VDC VOLTAGE. If you DO NOT see this then there is a disconnect somewhere between the battery terminals and the +BAT terminal on the 12VDC Distribution fuse panel.
This is a WF8900 series 12VDC FUSE PANEL showing where the +BATTERY connection is at. The LARGE WHITE CABLE on the top double lug connection is the -12VDC (NEG) cable going to the battery. The LARGE BLACK CABLE on the bottom double lug connection is the +12VDC (POS) going to the battery.
The TOP double lug connection HEAVY WHITE WIRE to the left goes to the 12VDC connection on the WFCO Converter/Charger unit. The CENTER LARGE WIRE LUG with the RED CABLE is the +12VDC connection going to the converter/charger unit. This is where the converter/charger unit connects to the 12VDC Distribution FUSE Panel to also provide power to the 12VDC items connected to the panel. This also provides a charging DC VOLTAGE for your connected batteries when shore power is connected. Right now however you should only be concerned with why the BATTERY POWER is not being measured on the top and bottom double lug connection point when the shore power is turned OFF.
The only thing between these two points on the 12VDC Distribution connections and your battery connection is an IN-LINE FUSE mounted close to the BATTERY TERMINALS or maybe a RESETTABLE 12VDC AUTO-RESET CIRCUIT BREAKER.
You to do some hand tracing of cables between these two points to determine where the disconnect is. It could also be a BATTERY DISCONNECT SWITCH has been installed breaking the POS wire connection. It could also be a BAD terminal connection at the battery terminal. Once you get the 12.6-7VDC readings here with your multimeter then things should start working the the 12VDC FUSED DISTRIBUTION PANEL is controlling.
Another item one should check again is when you have removed the battery connections for what ever reason you may not have put the cables back in the correct order. The best way I have found is to find the PRINTED word NEG or SYMBOL '-' on the battery CASE and make sure this is the battery cable that goes to the trailer frame ground close to the batteries. If the battery cables have been reversed or sparked together etc you probably have blown the IN-LINE fuse close to the battery and two fuses on the 12VDC Distribution Panel that are off to them self in the above 12VDC panel photo which are the REVERSE POLARITY FUSES.
CHeck back on here when you have 12VDC at the top and bottom double lug connections on the 12VDC Distribution Panel fuse board.
If you do not have a multimeter they are very inexpensive from WALMART/LOWES/AMAZON/Any number of Auto Parts stores ($7-$25). Actually HARBOR FREIGHT will give you one for the asking when you purchase other things from them. This is a must have item if you want measure your actual 12VDC and 120VAC connections in your trailer.
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