I bought this stereo from a pawn shop 4 years ago, they tested the unit in the store and it functioned well. Now it's time to install it, when I connected the harness to the stereo it blinks 4 times with a faint view of what should be displayed when the stereo is on. When I close the face the screen does not display anything, it looks as if was powered off. I can insert a CD and it does play, but when I close the face I cannot Control anything because the of the black screen. I've already pressed avery button while the CD is playing and I get nothing. Thoughts???