97 Dometic fridge question

Hello. I have a 97 model 5th wheel with a dometic refrigerator. There is an ac light right by the on/ off button and there is two other lights by the other button. Auto. Gas. When I am plugged in to shore power the auto and gas lights are lit I push the button and it changed to just gas.....I was confused because when I switched my battery charger breaker off then I pushed the button again with both lights lit and it changed to just auto but then the AC light came on as well. My question is why if my battery charger breaker is off am I able to run fridge on AC . I suspect that it does not run through the breaker at all then correct? That is what I concluded. But my main question is then why if I'm set to auto did I have to turn off the battery charging breaker of my converter and then push the button in order for it to turn to AC mode making the AC light turn on? It would not otherwise get ac mode to turn on. Please help me clarify. I greatly appreciate it.