I have almost successfully installed a new radio/CD player in my Son's 1998 C280. However, I can't get the speakers to cooperate. I know the radio is putting out sound (wired a spare speaker to radio output wires and got music), however, something seems to be muting the car speakers. There are extra wires from the old factory radio that I can't identify their purpose. The factory radio must have had a built in phone or something in order to have these extra wires. I've read something here about faders and extra wires from those? I tried touching a 9v battery to many of these "extra wires" including the ones I'm pretty sure are the real speaker wires but I don't get any sound at all. I just think something is muting all the speakers at once. Help! My Son is tired of riding around college with a brand new radio sticking out that won't play!

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1999 C230 Kompressor
1998 C280 Son's car
1999 C280 Totaled by other Son