Apparatus for conveying air to radiators of motor vehicles and the like having a fan (10) having a plurality of blades (12) each radially mounted its own coupling device (31) on a central body (11) and able to be rotationally actuated about its longitudinal axis by an actuator (41,42,43) depending on the quantity of air required for correct cooling of the fluid, the apparatus has a device (60,160,260,360,460) for engaging/disengaging the transmission of the rotational movement from the drive (23,21;321a,21;421a, 21) generating movement to the fan (10).