It flickers ever so dimly and then goes black again.
Yes, that's certainly a concern then because usually when you have an issue with NAV system it freezes and the Nissan symbol stays on the screen and it won't change. You can usually re-initialize the system or update the software to fix it.
The fact that yours flickers and goes out is a good indicator of the problem being internal to the unit itself.
I would approach this differently then your dealer would though. I would start be disconnecting the battery and holding the terminals together for 5 minutes to reset the modules and reboot the NAV system. If it fails to work, I would then send the NAV system off to be repaired, which will cost around $500.
In the U.S. we have OEM audio/NAV places that you can mail the units to for repair, you don't have to replace the entire unit.
Do you mean holding the battery terminal cables together for 5 minutes? I disconnected the 4 screws holding the Connect system in place to see if I could get it out to check cables but the whole dashboard unit loosens and not just the connect system. I tried to pry this out but couldn't move it and didn't want to force it, is there a trick to getting it out?
Yes, I was referring to the terminal cables. This drains the modules and forces them to reboot.
The whole panel will come off after the screw are removed.
The plus cable on the Nissan battery is very short with no play in it and I am very nervous about stretching the minus cable over the plus battery terminal in case I short the battery so I thought I would try and disconnect the unit instead and short the power input cable but after removing the 4 screws I couldn't budge the panel(its loose but wont come out). There must be something holding it back and I can't see what it is. Any ideas?
The sat/nav unit sits in a large dashboard panel with air vents and this whole panel comes loose when unscrewing the 4 screws but although it is loose it feels like there is something holding it in place at the top of the panel(closest to the windshield). How do I get the sat/nav unit out?