A method and device for assembling a composite housing fitted with a shaft and at least one associated mounted element are disclosed. The method may include the steps of: arranging the housing in a predetermined position with respect to an actuator; arranging the shaft in a predetermined position with respect to the housing and the actuator; selecting a mounting element to be mounted on the shaft; conveying the mounting element into a predetermined position within the housing; pushing the shaft via the actuator so that the shaft passes successively through an opening of the housing and an opening of the mounting element; and positioning the mounting element in a position adjacent to a heat source for a predetermined duration after the step of selecting the mounting element and prior to conveying the mounting element.