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.
Car Problem Reports
Mercedes-Benz C320 4MATIC Broken Stepper Motor Actuating Arm May Cause Clicking Noise From Behind Dash
Mercedes-Benz C320 4MATIC Problem
Average Mileage: 120,152 mi (100,000 mi - 150,000 mi)
Visitor, 2003 Mercedes-Benz C320 4MATIC
I heard the problem months ago and now have little air flow from the upper part of vent. When AC is on the blower is working at feet level but very little air movement in upper vent.
Visitor, 2004 Mercedes-Benz C320 4MATIC, 119,500 mi
When I start my car, I hear clicking sounds (8 to 9 clicks)