One method of determining if the converter is charging either the coach or chassis batteries when on shore or gen is to buy yourself an inexpensive multimeter (use the voltmeter function) and carefully measure across each battery when charging; and use/store is on. if you measure approx 13vdc or higher, under light DC loads, then you should be good. Note that some coaches have battery charge control systems that monitor voltages on these battery strings and may not connect the strings together, for charging from converter, for several minutes.
Just to add, some coaches may not be designed to charge both battery strings off converter......I want to say MBenz chassis based units, but my old memory could be very wrong. I am sure someone will clarify this.