Abstract: An air vent that automatically opens and closes in response to changes in the ambient air temperature. The air vent includes a housing, a louver frame mounted to the housing and a series of vent louvers pivotally mounted to the frame. The louver frame includes a cam member for automatically pivoting the louvers between an open position and a closed position in response to ambient air temperature changes. The cam member includes a spring fixedly mounted at one end to the housing and mounted at the other end to a camming bar, which is mounted to the louvers. This spring is formed of two different types of metals which react to changes in the ambient air temperature. More specifically, the metals are chosen so that the spring expands as the temperature increases to rotate the cam bar in one direction and incrementally open the louvers, and contracts as the temperature decreases to rotate the cam bar in the reverse direction and incrementally close the louvers.