Audio Systems: my CD changer is messed up, volkswagen cd changer, ebay

Question
I bought a 98 GTI with an aftermarket Sony 10-disc changer already installed. It has a wired lcd-display device that controls the changer in the trunk and a remote control for the wired device. The wired device uses 88.3 on the FM. I didn't install it myself so I don't know how it is powered, but when I turn the accessory the backlight goes on, but the wired device rarely works. Sometimes, after the car has been on for a while I can press the play button and it will turn on, but the slightest bump will often turn it off. Sometimes it can be turned back on immediately, sometimes not for a while, sometimes not at all. It's extremely unreliable. I'm fairly electric savvy and I can fix most problems myself, once I identify them. Any suggestions?

Answer
the ground wire  is lose on the cd changer and is taking ground from the antenna   this cable is behind the stereo

that vehicle is prewire for a cd changer the cable is in the  left side of the trunk  and you don't need no displays all the cd information shows on the radio display
i just sold my volkswagen cd changer on ebay for $90.00 you can find one there  
in case the ground is not the problem