In Summary
  • That sort of noise could also be caused by stuck air conditioning vent flaps due to a broken down vent flap motor.
  • This problem is randomly found in used W203 and W163 Mercedes Benz vehicles built between 2001 and 2004. It also happens to other vehicle models with automatic climate control systems. Recently I saw it in a 2004 Toyota Harrier. The stepper motor or stepper motor linkage replacement is fairly easy because it is located in the foot well area (above the pedals).

Hi Paul, I enjoy reading your car articles. I have an irritating problem on my recently bought Mercedes C Class 2003 model. When I start the car, it makes an audible ticking sound under the dash board for about 20 seconds. The noise sometimes repeats after some minutes. My mechanic cannot tell what causes this noise. Besides, my AC seems to be on and off. What could be the problem? Merina Balungi.

Hello Merina, the repetitive cycle of clicking noise which you hear from the centre of your dash board when you start your Mercedes Benz or switch on the air conditioning is usually caused by a broken stepper motor actuating arm or the foot well damper linkage. The actuating arm regulates directional flow of air in the climate control system.

That sort of noise could also be caused by stuck air conditioning vent flaps due to a broken down vent flap motor.
This problem is randomly found in used W203 and W163 Mercedes Benz vehicles built between 2001 and 2004. It also happens to other vehicle models with automatic climate control systems. Recently I saw it in a 2004 Toyota Harrier. The stepper motor or stepper motor linkage replacement is fairly easy because it is located in the foot well area (above the pedals).

The vent flap motor or vent flap linkages are more tedious as they involve a partial dash board dismantling to access. A knowledgeable Mercedes technician with the right tools should be able to identify what has failed.
Replacement parts can be bought or ordered from the local Mercedes dealer.