I have the same audio system. A,B and C are the 3 zone choices. One is for bedroom, one for outside and one for living area...if your trailer is wired like mine.
I turn off all power when I leave trailer so I lose radio memory. So I need to turn off the outside zone everytime I turn power back on. In my trailer, I turn on radio and turn off C zone. Simple.
2015 Sierra 1500 Denali
2014 Coleman 249RB
David Jon Devoucoux
People, Places & Things...for over 40 Years!