Smartnav Touchscreen

[roadwarrior]

Hi can anyone help?
I have a Smartnav unit That was built into a case to make it transferable between vehicles. I recently purchased a touchscreen and fitted it to the unit in the case. When i turned the smartnav on the screen displays the welcome message and then says connection error.
A piece of paper with the screen said that if this message appears contact the smartnav helpline. This i did and was told my unit needed to be software upgraded. They have carried out this download several times but i still get the error message. I have checked and rechecked the wiring from the screen and have continuity between both units. I noticed there are three wires in the smartnav unit not connected Brown, purple and white, but these have always been there. Are there any techies who can help me out?. Thanks in anticipation

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