I have been experiencing problems with mine. I lost video but still had sound, bought a new camera and I have not been able to get either to sync.
If you remove the sealant from the wire going into the roof there is a plug in there to unhook the camera. You can pull the wire out far enough to get to a pair of wire nuts. This will allow you to test for power.
I believe they have power running to the camera all the time and it is burning the cameras out. I pulled a wire from the back patio lights, this allows me to turn the camera on and off and light the back when I do need the camera at night. Some use the camera while driving, I do not.
I called the Tech's and they sad all you can verify is whether or not you have power to the camera. Then at that point you either have a bad camera or monitor. They are telling me mine is probably a bad monitor.
I asked if I could send them in to get it fixed and they said if it is not under warranty they would only sell me a new one if it does not work. Their Customer service sucked. I am thinking about buying one of the magnetic cameras and just putting it back there when I need it.
2014 Voltage 3950 Epic III
2016 Ram 3500 Diesel 4wd, Long Horn Dually long bed