1: The volume does not seem to be adjusting with speed. Is there some way I can tell if it is disabled, or is there even a way it can be disabled/re-enabled?
2: When I'm listening to a CD with the CD changer, is there anyway I can have the power antenna in the down position?
That used to happened with me. I used to have the volume at one level on Monday then on Friday it's louder. Also it did not adjust according to the speed you're driving.
The reason. The volume control will start to fail. The MB Tech took my Radio out and clean inside with a electronic cleaning spray. It worked for a couple of weeks untill it did it again and i changed it to a Pioneer.
At the dealer they showed other C-Classes which has the same problem. It looks like when these MB (Becker) Radios get old the volume control is worn out. Also the volume knob which is made out of rubber start to breal apart and it feels sticky.