Instrument panel having coaxial knobs for vehicle heating or air conditioning unit

The control board has three concentric control buttons which operate electrical contacts and valves. An internal button (20) is directly connected to a disk bearing electrical contacts and an intermediate button (9) operates an air valve through a pinion (34), a worm (36) and toothed sector (37). An external button (7) also operates an air or mixer valve through a pinion (41), a worm (43) and toothed sector (44).