The CD changer may suffer from an internal mechanical problem. Replacement of the faulty unit is generally required to correct this issue.Google+
Car Problem Reports
Mercedes-Benz C240 CD Changers May Suffer From Internal Mechanical Problems
Mercedes-Benz C240 Problem
Average Mileage: 69,833 mi (30,000 mi - 145,000 mi)
Visitor, 2004 Mercedes-Benz C240, 43,000 mi
cd changer is being replaced...... when i press cd button screen say "no magazine" when it was inserted
Visitor, 2003 Mercedes-Benz C240, 70,000 mi
"No CD" message; Won't eject magazine; will occasionally work by rapping on magazine.
Visitor, 2003 Mercedes-Benz C240, 145,000 mi
Problem since about 60,000 miles. I could coax it into working by rapping on the cartridge until recently.
Visitor, 2004 Mercedes-Benz C240, 30,000 mi
cd will not operate. says cd not installed.
Visitor, 2002 Mercedes-Benz C240, 68,000 mi
Won't play a CD, won't eject the CD's