I installed Haloview rear view cameras on our travel trailer powered by the clearance lights and everything worked fine powered from the RV battery. Then plugging into a Mercedes GLE350 the cameras were dead, but clearance lights worked fine. Plugged into a pickup truck and camera and lights were fine. Checked voltages at camera and they read required 12+ volts for both truck and MB. After much internet searching with no solution found I concluded MB was doing something screwy with the clearance light power so I jumpered direct battery to lights and cameras now work. Some more research revealed that Furrion camera make a special jumper cable to "bypass the vehicle computer". Apparently some new vehicles are 'smart' and mess up simple DC power circuits and are so clever a simple voltmeter can't spot the sabotaging signal on the line.