ac/heat air doesn't come from the middle vents,only side ones, why? on 2000 Mercedes-Benz SL500

no air blows from the center vents.Was told it's a sensor. Where is it located?

Asked by for the 2000 Mercedes-Benz SL500
If it's the air blend sensor in the the ventilation distribution assembly it is not easy to get to. The majority of the dash board assembly needs to be removed to access the sensor and replace it. I recommend having a professional do this for you because of the extensive amount of work this requires.
Thanks so much. This has turned into a very expensive toy.