I know this is a well covered topic but i cant find any post's with the exact same problem. My c class had the steeper motor linkages fixed about 4 or so months ago and then about three weeks ago the sound came back but this time it only happens when it is cold and i am starting the car in the morning. it clicks for a while then stops. i can change where the air comes from and do the motor sync with no problems or noise. any ideas or do you think the motor itself is what is wrong?

 

https://mbworld.org/forums/c-class-w203/177068-noisy-air-conditioner-stepper-motor-replacement-clicking-hissing.html