Hi, in the last 38 years I’ve had various Opel, Ford, VW and Mercedes vehicles, and in the case of all vehicles without exception, after a vehicle age of about 7 years, the interior fans became noticeable by noises (mostly a whistle). This raises the question of whether components of inferior quality are installed here a) in order to save costs or b) the market for interior fans is so narrow that the few suppliers do not need to deliver quality. and you are closer to the topic and can write something about the causes?