I JUST RECENTLY PURCHASE A ML 320 2003 ..WHEN I TURN ON THE RADIO... CD..... OR NAVIGATOR ...THERE IS NO SOUND AT ALL......EVEN A HUMMMMING SOUND IS NOTHING.........I DONT KNOW MUCH ON THIS... PLEASE HELP....... BUT THE STATION ON AM OR FM WORKS FINE.... NAVIGATION WORKS FINE TO..... JUST DONT HAVE A SOUND..... FUSES ARE GOOD AND ALSO CONNECTION ON THE BACK OF THE SYSTEM ARE GOOD ALSO. AMPLIFIER ARE GOOD TOO.......................PLEASE HELP