The owners manual explains things in a way that I dont want to hear. 
I will try to explain in detail what I want to do.
2003 Ford Excursion with factory overhead DVD. I will do all my standard connections. I have identified the wires on the factory Ford harness that output audio from the factory overhead DVD system. (orange/black trace, grey, green/red trace, purple.) I was going to hook RCA leads into these wires so I can get audio from the factory overhead DVD system into the x930. (Video appears to be a much bigger challenge - if not impossible.)
At the end of the day, what I want to do is this: be able to play video from the factory overhead DVD player on the factory video monitor. This part already works. Here is where I am choking - I want to be able to feed ONLY the audio signal out of the factory overhead DVD player into some input on the x930. I assumed this would work. It would allow the video signal to work like factory but I wanted to be able to use the dual zone capability to be able to pipe the AUDIO ONLY to the rear speakers.
Unfortunately, the owners manual states the following in regards to dual zone:
"When 'AV1' or 'AV2' is selected, the following restrictions are applied to the rear display.
- The video image and sound are output only when 'AV1' or 'AV2' has both video and sound.
- The video image and sound are output only when the corresponding setting on 'AV1 Input' or 'AV2 Input' are 'Video' "
The bolded line above is my sticking point. I will not be able to feed video into any of the inputs, because there is no current way to get video signal OUT of the factory overhead DVD. There IS an easy way for audio, but no way identified for video.
Are there any inputs that will accept AUDIO ONLY and be able to be selected for use in 'dual zone' mode so I can just have that audio play over back speakers without having a video source input into the x930?
Halp! Thanks!
Zach