It's good to change the filters regularly. They are cheap ($15 or less from Pelican) while expensive ($40 or more) from a dealer. My last one was in the car for four years, during which I drove only 16,000 miles; it was clogged from that driving.

I put a new one in about a month ago, and the fan immediately ran at lower speeds. It took me about a half hour to change it. Instructions are in the box. I think one of the reasons for fan failure (which happens regularly in the W 210) is failure to change the filter.

OK. That was pretty easy. The new part is beefier looking than the old one.
Fan blows full speed.