2011 e class convertible... aps 50

[Frosty149]

1st Consult the audio manual and as mentioned above the engineering menu settings (see YouTube ‘secret menu’) but be careful what you alter, keep a note of the existing settings before altering, so you can revert back as needed.
As Cowley above, you may have a faulty unit....

 

[Heyboss]

Thank you