Yes it is black & White rolling picture , I thought the nav was NTSC but when I get the picture on the screen it turns over to pal ???

Yep something like that. About £10 on eBay. Before you buy, find out how the monitors are wired. There is possibly an amplified splitter in the car already, since you have two monitors fed from one feed.

Alternatively, each monitor may have a video out, and then you would have a spare video out on one of the monitors.

OK so one option is to go with this and this.

The splitter amp would permanently feed the AV IN for the front screen, and the 2:1 switch. The other outputs are unused.

The 2:1 switch would be fed with AV OUT from the GPS.

Hence front seat passenger can select AV IN to see the DVD.

Rear seat passengers would toggle the 2:1 switch to see the nav or DVD.

I couldn't find a 2:1 switch with a neat looking remote button, but I'm sure they exist.

If there is a space video audio out on the thing that feeds both monitors then you won't need to use the amplified splitter.

No the RCA cable coming from video out has two cables in one they just split to each screen

Hey I've just bought the first spliter 7.99 hope it will work , will that give me DVD player on the nav ??

Yarp. But you need to solve the NTSC/PAL issue. Have a google around to see what the TV tuner AV IN and OUT work on, it's probably NTSC. Jochen will know. Obviously you want to standardise on something so everything works.

Have a play with the menus on the DVD player and TV tuner to see what you can do to switch to NTSC for everything without breaking the rear screen picture.

Look what I've found
http://tapatalk.com/mu/021abebb-ed94-677d.jpg

Any good

That is not the right thing for you because those AV in out pins are already in use. They connect to the centre console. You could buy it but fitting it would disable the centre console pins. It's also a lot of money for some parts that are available for pence and pounds at RS and Farnell.

Yeah I know but I've cut the back off the av in/out !!!!!!