avic z2 rear camera

Hi All, I have a 06 ford f250 superduty with an Avic Z2 and a Boyo licence plate camera. Earlier this year the wire harness going to the camera shorted and melted the connector on the back of the head unit. I replaced the stero and camera, made my own wire harness from 18 gauge and now everything works great. My question is there a way to prevent this in the futuer say with a diode or something? I believe the video and hot wire on the old harness is what caused the failure. Any help you could give would be great, I'm very new at this and not sure what to do. Thanks

Is it a 4 wire plug? 2 for power and 2 for video signal? Add a fuse to the power supply to the camera close to the head unit.

Thanks for the reply, it is a three wire plug; 1 12volt, 1 ground and one video. what size fuse do you think would work? Also would this take care of any damage to the unit if say the 12volt and video chaffed to each other somewhere in the frame? Thanks again for the help. Cheers