Enging charging of your house batteries does not involve the Magnum Inverter/converter panel.. It will normally be in INVERTER mode when driving down the road..
how to see if engine is charging batteries method one
You need: A digital volt meter
With engine off, Shore power off, inverter off or on (off is best) measure voltage on the HOUSE batteries..
Start engine, wait one minute, Now re-check the voltage on house batteries
12.6 = Full, Resting. 13+ = Charging. (also full or near full)
NOTE: if the starting voltage is LESS than 12.6.. then any increase = charging.