[VACList] 12 volt dc circuit

[<kkm7726@xxxxxxxxxxxxx>]

i just started rebuilding a 1964 24ft international airstream.  i have a 
problem with the GE converter,  i think its origional, its not charging 
the battery when hooked to 120volts ac.  the converter works the 12 
volt lights inside with the battery disconnected.  this tell me me 
converter is putting out dc voltage. four wires come from the 
converter going into a metal box which has two switches on the front 
with a small 120volt bulb.  can anyone tell me what this box is for 
also why the converter doesnt charge the battery.  the two switches 
are marked,  city power and battery power.  everything works the 
same with the switches in either pace,   four wires come from the 
converter to the metal box and eight come out and go into the wall.  i 
dont guess any one would have a schematic  thanks  DAWSON