I'm having trouble figuring out what is causing this constant buzz in my front passenger speaker on my 560. The noise is audible as long as the radio is on and definitely only comes out of the front passenger speaker in the dash. It does not change with volume or engine RPM. In fact, if I turn up the volume high enough, it is hard to hear the buzz.

The speakers are original and the head unit is a Becker 1480. It was rebuilt about 5 years ago and has the auxiliary hook up added in. I even swapped in a speaker out of my 420 parts car and it still is making the same noise. What could be the cause of the noise?

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1998 E320 Wagon

1992 300D 2.5 TURBO

1991 560SEL M119.960

1986 300SDL TURBO

1992 500SL Parts Car

1991 420SEL Parts Car