Audio but no video when playing dvds

I had this problem, u need to earth a single cable, i think its either brown or green, basically the system wont let u watch films while driving, so bring up the screen which says (parking off) n touch the wires to some metal until it switches to (parking on) shud work then

Maybe there is a break in the cable internally that supplies the video, try another interconnect lead that you know works and we can then take another look at it if there is still a problem