just bought a c class 203 and i noticed that when i put down the driver's side window there's a slight sort of crunching noise. it's very faint, in fact when the stereo is on you dont hear it, but when it's quite you can hear it sort of crackling, only when the window is going down not up. any idea what it might be please? the winder perhaps? should i repair it now, or should i let it get worse first?

 

You need to remove outer sealing rail and clean it up from dust. Use dust remover spray and rubbing alcohol for rubber part. Before reinstalling outer sealing rail, run the window up and down a few times to check if there is any bad sound. Taking off outer sealing rail depend on model and it is tricky.

 

thanks platonmind, managed to remove the outer seal and did what you said with the dust remover spray, the noise didnt go away completely but it is much better now, hardly noticeable, thanks!