Air condition on 2000 Mercedes-Benz S500

The ac is working great The problem is Driver side vent is not letting the cool air out warm air is comming through the went
What could be the reason?

Asked by for the 2000 Mercedes-Benz S500
Sounds like an air direction motor on your Driver's side is not working properly. Best to have your Climate Control Computer scanned to determine what are the air flow control problems that need to be addressed.