I couldn't find any option to increase the airflow in the center back of rear passenger vents.

 

Most of us here share your disappointment in the amount of airflow serving our rear seat passengers. There's been a few discussions on this in the past, here's a link to one of them: https://mbworld.org/forums/new-s-cla...back-seat.html

Reducing the airflow through the front vents (via the vent thumbwheels) does push more air to the back seat area, but it's still not that great...

John

 

I have closed all the front vents.....and it's still minimal in the back....pretty retarded