64thunderbolt wrote:
it is a 5th wheel. It has no park. with the tow vehicle unhooked what would the stereo interfere with? I am getting confused how a stereo in a trailer would interfere with the tow vehicle.
You can reread the posts but I'll try to explain it again. Some head units have a defeat built into the unit. Video playback is defeated unless the head unit gets a signal that the vehicle is in Park. That defeating can be bypassed by installing a jumper or a couple of jumpers into the connection on the back of the head unit. This "tricks" the head unit into thinking that a vehicle is in Park and video playback is initiated. It has nothing to do with your tow vehicle and is all about the head unit. It doesn't matter that you're installing it in a trailer, the head unit still needs to be sent that signal through the connections to operate video playback.
If you are just playing the radio, it should operate as typical but a DVD won't play.
Since you are unaware of this functionality, there may be other things about installing a head unit in a trailer that you also don't understand. Those could be how to get the signal to your speakers so that you can listen to them and also how to make a DVD play to feed your screen.