A repetitive clicking noise from behind the center area of the dash panel is usually caused by a broken stepper motor actuating arm. The actuating arm controls the direction of air flow in the climate control system. Disassembly of the center console will be required to access and change the broken arm with the updated, reinforced part.Google+
Car Problem Reports
Mercedes-Benz C32 AMG Broken Stepper Motor Actuating Arm May Cause Clicking Noise From Behind Dash
Mercedes-Benz C32 AMG Problem
Visitor, 2002 Mercedes-Benz C32 AMG, 150,000 mi
Used to click from behind dash when started after several attemps the clicking stops. Now it doesn't click anymore but I can't get air to the front vents. Need to replace but haven't done so yet.