Center Vents on W211 - Airflow

[MACHBUFFET]

Hi Folks
I've just changed car to a 2006 E320cdi Sport with the Thermatic (rotary temp selectors) and the operation of the center vents are a bit of a mystery to me.
Sometimes there doesn't seem to be much airflow through them, even though the side vents are full whack. I'm assuming that the airflow is controlled by the wheels and the winding fully in the direction of the arrow is full open?
However, someone hinted that the operation of this control wheel also affects vother vents in addition to the face level vents.
Any pointers gratefully received.
Thanks in advance

 

[someman41man]

Have you selected the center vents using the "mode"
button

 

[MACHBUFFET]

Yep, I've selected the mode control as required but there still doesn't appear to be as much "puff" coming through the center vents as the side vents for instance.
Also, as I run through the modes, I can hear the blend doors moving but sometimes for instance with the foot vents, they don't always shut off when a different mode is selected - or they take a while to shut off.

Thanks

 

[donubenz]

Hi this heating system is really sophisticated and it is worth a read in your manual. e.g. if you hold the recycle button any open widows and sunroof will close and hold down again and they will return open. The key can be used to open windows if you keep the open car button down etc.
The middle wheel with blue colour on will bleed cool air in on full blue. To keep cool fresh air blowing and keep you alert! The end central wheels just open or close the individual vents. To test, run the mode to the mid point and override the fan to crank that up manually on the buttons. If you turn off the outer vents near the doors a gale should be blowing at you if this is what you want? The system reasons that you may not want a fast blowing air stream on your face and adjusts it accordingly. I find unless my hands are really cold and I need hot air on them that the auto setting just works all year.
Enjoy the car.

 

[prprandall51]

On the centre vents, there is a position on the rotary wheels just short of fully open that directs most of the air to the large central defuser on the dash instead of the vents themseleves - to achieve draught-free ventilation. When the wheel is fully open all of the air comes through the vents.

It is bizarre behaviour, I am not sure if it's in the handbook.