Hi kennyhwa,

Just to let you know, I service all Mercedes radios, changers, etc.. I have found that the Vol. control will go bad on your radio by first becoming unstable by not working everytime you move it. At first it will work only if you move it slowly but then even that will not work. The control in your radio is not a normal type of control. It is a digital control type and works completely different from the non digital type in that it adjusts the volume using a HEX control not a potentiometer. I can repair your unit when you get tired of fooling with the control or when it gives up on you. It runs under $100 to get done, which is less than factory repair and it comes with a new knob. If I can help you or anyone else with this type of problem feel free to contact me via my WEB Site at: www.lajollaaudiorepair.com

Cleeve Morrison
La Jolla Audio Repair