I have a 2000 Mercedes S500 (W220) with a Bose amplifier in the trunk linked via fibre optics to the head unit, and a CD changer also in the Trunk. Everything works fine in the navigation unit inside the car but NO SOUND. This problem started when WATER got underneath the unit in the trunk and the CD changer also stopped working(The NAV Screen does not recognise the CD changer and the PhHONE) . I bought a new AMP and there is still no SOUND

 

the electrcal connections are probably corroded.. sometimes pulling the fuse for the radio and amplifier will do the trick. but if you got water in there youve got other issues.