new stereo

Thanks the only answer that makes sense. No video just a simple automotive stereo. and the wall unit was only using the right side speakers going to the switch for different areas of the trailer. Without the Video I would think it has no park wire. Wiring diagram is the same as the unit I removed. The only diff is the orig was only using right side going to the selector switch that routes the sound to bedroom, living room, bedroom+living room, & outside. I just installed the same unit in my F350 & my Toyota Corolla with no issues. It's not rocket science but I am having issues with the trailer.

The wall unit has an A & B switch but B is dead and A works because the unit is only using 1 side to go to the selector switch.