I know this thread is 8 years old, but I've developed exactly the same problem with my 2016 car.
When the air conditioning is on 'recirculate' I get a loud knocking noise coming from inside the centre of the dashboard. It seems to be a fan hitting something.
When I turn 'recirculate' off, the noise stops.
Could a fan be hitting some kind of flap? Did anyone find out what causes this knocking noise?
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'03 Grey >>> '06 Black >>>'10 Silver >>> '16 Grey ^
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