I ran Navman for some 2 years, now sold and obviously the manuals went at the same time, so I cant quote word for word.
I recall from new - or when you do a 'factory reset' it disables the position output for the DSC VHF. So this may be worth checking before you change any wiring already made.
I had power feed problems (at one point) where I had to do a factory reset every time I repowered it up, so I went through the set-up quite frequently.
The radio GPS would show position and the radio would say 'no position'.
It is detailed in the manual - I believe when you get to the correct menu it also asks an 'autopilot' enable question either above or below.
Good luck getting it going.
If you are interested I have a full home PC planning kit for C-map