You don't have to do anything outside. Pull the radio inside the camper, find the wires for all the speakers connected to the back of the radio and correct the wiring. Your radio is wired with the pair of speakers that responds to the fader wired backwards. the two outside speakers should be wired to rear output, right and left, and your two inside speakers should be wired front output, right and left. Someone crossed a set of wires when installing the stereo. There should be a wiring diagram with the Kenwood manual that will at least show you Kenwood's color code for wiring. no guarantee that the camper manufacturer followed those colors though, but it should be easy with a meter to tell which wires are which. This is a 20-25 minute job tops for someone who is familiar with car stereos.
