Heating or air conditioning installation for a motor vehicle

The heating and/or air-conditioning unit (10) has a housing (22,32) provided with a number of parallel shafts (24b,25b,26b,27,34b,35b,37) around which valve bands (24a,25a,34a,36a) are passed, several valve bands passed around a common central shaft (27,37) around which the other valve band shafts are spaced. The central shaft and/or one of the other valve band shafts can be operated by a rotary drive.