ok so my buddy had to jump his car the other day and some how f*&^ed it up. He fried his face unit for sure, but how do you know if its just the face unit, not the wires behind it or the big ass unit?
if the problem started after the car was jumped most likely a fuse has blown. if you have a digital multi-meter set it to read Ohms and test each fuse. otherwise, pull the radio/interior fuses and replace blown fuse.