The invention relates to a ventilator for an alternator-starter, fixed on a rotor (4) with magnetic poles and comprising: a metal insert (13) which is used to fix the ventilator to the rotor; an end shield plate (17) and ventilation blades (12) which are made of a plastic material and which are moulded on the metal insert; a magnetic target (14) ensuring metal follow-up of the rotation of the rotor with the aid of at least one associated rotor.
