sony md changer and xav-7w problem

Any one knows where can i get i replacement for a sony in-dash monitor, i need the wiring harness, i tryed the sony store but they don't have it, the problem with my harness is that the ground & power wires became lose, so the in-dash won't work properly (turn off constanly) , any one know how to repair the harness, also any one has same problem with this unit. the wire i talking about are the ones in the harness that connect to the back of the unit.

I have been having trouble with my unit for some time now. Well if anyone is familiar with this particular unit-this unit has basically two parts.The bottom has the control buttons on it(vol.,source,search etc.) and when opened is the monitor. When closed the top part is where all the information appears(track number-station etc.) Well this unit works perfectly but after a couple of times that i turn the car on and off(usually with more than 4 hour breaks) the sound will come on but the display screen will just turn completely black-and if i try to open the monitor -that too also just comes out completely black. I have tried pressing all the buttons to get the displays to come back on but the only way i have found is by pressing the reset button on my unit, some times work sometimes doesn't.

first i replace the wiring harness, which i tougth was damaged, didn't solve the problem, next i purchase a new unit same brand and model, replace new wiring harnes and all cables, (rca, connection box cable,) still  i have the same problem,  i am about to lose my head, i have been working for almost a week on this and can find the problem, i already  change the gound,  but still doesn't work,  is so strange because radio works,and  the input where the PS2 is plugged they wok, sound comes throuth the speaker but the screen is black no illumination is display, only on the bottom potion of the unit, the buttons they ligth up, but any of the screen will turn on (small screen were time is diplayed- and large screen when it opens)  so any one that know what migth be causing this let me know what  can i do, i check fuses , power , and harness, but they are all ok. and i am sure the HD is not deffective, here is more info that can be helpful . this is installed in a 1999 lincoln navigator ,

i am sure the HU is not defective because it is the second unit that i installed on the same truck and they both have same problem, But i finally found the problem, the F****in problem is my mini disc changer when i plug it in, the screen will turn off and illumination goes off, after i unplug it and reset the unit it will turn back on again.  It is connected trougth the buzz link or i link , (not sure what it is called) the cable the sony used to control cd changer and mini disc changer. that the only cable that makes the changer to power on and the rcas send the audio to the unit.

so any one with experience on sony pruduct , why is this happening? do i have  a defective changer or i don't have enough power to run the md changer, i was thinkin the there wasn't enogh power because the stupid people at the shop i took my navigator to get my head rest monitors installed they used the same wire that my unit  used for power to power all for monitors.  i so confused because all the monitor work fine , it is just the indash unit that is givin me problems , every time i plugg the md changer,  i will really apreciate your help