An air conditioning device for installation in a vehicle has a moulded casing enclosing a front air intake chamber, an intermediate mixing chamber housing a hot water heater through which a regulatable part of the intake air flows and rear air distribution chamber which distributes conditioned air between upper outlet ducts and a lower, regulated, outlet. Respective control levers controlling flow of hot water through the heater and the flow of air there through are housed in a box located in but effectively sealed from the air distribution chamber.