Necvox DA-7919 LCD Monitor Connection

[Notsoblurr]

Have bought the above unit and connected it to the Sony MEX-R1 DVD player. The above unit came with the following:

 

1) 1 video/audio input

2) 1 NAV input

3) 1 video/audio output

4) 1 CCD input

5) IR output

 

When I connected the Garmin GVN52 GPS Navigation unit to the "NAV input", there is no picture even when I set the input source to "GPS". The picture appeared when I connected it to the "CCD input" with the input source set to "GPS", but it will auto set to "CCD". I understand that "CCD input" is for the reverse camera.

 

How do I turn on the "NAV input" and switch off the "CCD input"?

Why is the reverse camera and the night switch signal using the same orange wire (I have connected the Sony HU dimmer wire to this wire)?

 

The wiring diagram attached here:

 

http://i94.photobucket.com/albums/l112/NotSoBlurr/NecvoxWiring.jpg