A ventilator (10) used for motor vehicle comprises a casing (12) made of plastic and at least one ventilating blade (14) which is molded on the casing (12) through injection. The casing (12) is provided with an opening (24) at the connection area of each ventilating blade (14). A mold for manufacturing the ventilator (10) comprises two cores (24, 26) which confine the profile of the ventilating blade (14) at the injection position. The two cores are used for demolding the molded component which is formed in the mold. In the injection position, an opening (32) is formed between two cores (26, 28) in the connection area of the ventilating blade (14). In the method for manufacturing the ventilator (10) with the mold, the ventilating blade (14) is molded on the casing (12) through an opening in the casing (12).