[DerPanzerWagen]

It's behind the glovebox on both LHD and RHD cars. It's a PITA to get to. And yes, it is normally the small plastic cog which breaks and it just makes this clicking noise as it tries to open/close the flap. (Even if you aren't using the recirc function!) Mine's been broken for years and is just left unplugged. Can't be doing with the hassle and have never needed to use it since.

For now, don't use the recirculate function. Best thing to do is to check the flap underneath the pollen filter and make sure it's set to the 'open' position. If you don't, when you run the air con it will make your passenger footwell soaking wet thinking you've blown the matrix. Then you can fix it at your leisure.

 

[DerPanzerWagen]

It's near the door side of the glovebox.