The radio in your camper is a car stereo. In most cars there are four speakers. You control the overall volume by the volume control. But there are also controls to adjust the volume side to side and front to back. The side to side control is known as the balance and the front to back is known as the fader. To get to the balance and fader controls you usually have to go into the settings menu.
Why have these controls? Say you have a minivan and want to turn down the volume in the back so the kids can watch a movie on the iPad but you and the wife still want to hear the stereo. You could use the fader to shift the volume away from the rear speakers to only the front.
It's a bit late tonight but I'll check my camper tomorrow and post the steps to access these menus.
Barry, MSgt, USAF, Ret. & Rose
2015 Nissan Frontier V6
2014 Coachmen Viking 17FQ