I've been getting this knocking sound behind my dash everytime I start my car and it would stop after a few seconds. I have been told the actuator motor must be replaced at an indicative cost of $2,500!
I've had this car since 2005. Is this actuator motor problem a current one in MB or other brands? Is it 'normal' that this component has such a short 'life'?
Thanks for feedback!

 

It is not the motor that goes bad. It is the plastic linkage that cracks allowing the motor to slip and the A/C flaps to slam shut. The part is not expensive but the labor is the problem. $2500 is crazy! I think it should run around $500-$700 at a dealer. You are told to remove the dash to replace, but you can get around this.