A heater control unit of a dial type installed on an instrument panel and functioning as an operation portion of an air conditioner equipped in an automobile. The first bevel gear is integral with the shaft coupled with a dial. The first and second supports are integral with the base member. The first support is sectionally crank-shaped and the upper support wall thereof is disposed at the outside of the lower support wall with respect to the second support. The upper support wall has an approximately semi-circular upper support surface for receiving a portion of the shaft upper than the axis thereof, and the lower support wall has an approximately semi-circular lower support surface for receiving a portion of the shaft lower than the axis thereof. The distance between the inner surface of the lower support wall of the first support and the inner surface of the second support is longer than the distance between an end surface at the second support side of the shaft and an end surface at the first support side of the first bevel gear. The distance between the inner surface of the upper support wall of the first support and the inner surface of the second support is shorter than the entire length of the shaft.