A heat-dissipating fan includes a casing having an air outlet, a base mounted in the air outlet, an impeller being mounted on the base and having a plurality of blades, a plurality of ribs each extending between the base and the casing along a radial direction of the base, and at least two air-guiding ring fixedly mounted to the ribs. The actuator unit is operated in at least one of the drive directions only if a corresponding polarity control signal is present and the control input is additionally supplied with a predefined control signal. A cooling system for a fuel cell stack in a vehicle that employs the noise-comfort function is also provided.