An articulated air valve arrangement in an air outlet of a motor vehicle heating, air conditioning and ventilation system has two vanes mounted for pivotal movement at right angles relative to each other. A single operator is slidably mounted on and pivotal with one of the vanes and is operatively unidirectionally linked to the other vane so as to effect pivotal movement of the one vane independent of the other vane on pivotal movement of the operator and, alternatively, the operator effects pivotal movement of the other vane independent of the one vane on sliding movement of the operator.