OK, again thank you for the excellent information. I would try GPS units in another car if I knew someone who was willing to let me test it. The two folks I approached on this forum who are local to me with NAV were not comfortable with this at all.
So... I think perhaps the TV idea is worth trying. How do I know if it's a multi-system tv? Does it have to be component input or can it be just single rca video input? Only green will work because it has sync? How do the other two channels (R,B) work? Is it something special with regards to the boardmonitor?
So on the blue connector pinout on the monitor harness (12 pin) which pin is Green? I guess I could just try each one until i see something...
So if WHITE means no video signals at all that would mean one of the following in order if what i think is least to most likely:
1) Both GPS units are not providing all 3 video signals (or will lack of only green signal cause white screen?)
2) Wiring fault in wiring loom for all 3 video signals (or will fault on just green signal wire cause white screen?) Is there a good way to test these connections with the multimeter? I was getting funky voltage readings on these wires even with car battery disconnected using multimeter in conjunction with a 1.5V AA battery. How does the 18-pin blue connector at the GPS unit relate to the 12-pin blue connector on the monitor?!
3) Problem with monitor (i.e. ribbon cable needs to be reseated - but would this not cause a blank screen?)
Another person from mp3car.com reccomended that I try powering up the display out of the car with no video input, if it stays white its definately a screen problem (makes sense), if it powers up but stays black then its not the display.
I am not sure how to do this, I assume i will need to supply a +12V and ground. Again I am unsure of the pinouts, is power supplied via white 12 pin connector, blue 12 pin connector or both!? I am thinking I might be able to accomplish this with an ATX power supply and/or computer case cables. I don't want to fry my stuff either lol
Thanks so much for your help. Any input is appreciated.