Ghost in the P.T

Okay, This is a strange one. The illuminated display of the fm radio sometimes goes out. The music keeps playing, but you can’t see the dial. (the same goes for cd’s too). When the display goe out, the horn will not work. If you mash real hard or just beat on the horn, it start working again, and the display will come back on also. I think this is weird. How are the two connected? This is hard for a mechanic to fix because it is intermittent. Sometimes it does this and sometimes it doesn’t. And of course it never does it in front of the mechanic. Can you please explain how the horn and radio display are connected???