Rear ventilation, function - GF83.10-P-2105-01GC

Function 

The louvered-type flaps in the rear vent open from the pressure of the air flowing through the vehicle and allow it to exit.

If a vacuum is present in the vehicle, as happens when driving with a window or the sliding roof open, the flaps close automatically due to the force of gravity. This prevents exhaust gases, dust and moisture from being sucked in.