Motor vehicle air conditioning

The system has a fresh air channel (5) for conducting fresh air from an environment of a motor vehicle. A circulating air channel (6) conducts circulating air from an inner space of the motor vehicle. A supply air channel (7) conducts the fresh air and/or the circulating air. A pivotable circulating air valve (8) i.e. butterfly valve (9), closes the circulating air channel and opens the fresh air channel in a fresh air condition. The valve closes the fresh air channel and opens the circulating air channel in a circulating air condition.