Heated air intake systems operate on the principle of increasing the temperature of the air. The fuel will more effectively stay in suspension in the air rather than falling out of suspension and forming droplets on the floor of the manifold. Warm air from the outside of an exhaust manifold is drawn up into the air cleaner to increase the air temperature as quickly as possible after the engine starts. The air cleaner assembly incorporates a thermostatic vacuum switch that responds to the air temperature after the air filter element and actuates a vacuum motor that moves the control flap to allow the air to be drawn from a cooler location such as the top of the engine bay or outside the engine bay. If the air becomes too cold, the thermostatic switch will automatically change back to drawing heated air from around the outside of the exhaust.