Hello everybody,

I own a C-Class W203, Year 2002, 220CDI Coupé Sport.

I would like to know what is this indicator located on the Air filter housing.
What is his function?

Seems to be adjustable

In advance many thanks

Best regards

Attached Thumbnails

 

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Present cars:
My car: E-class 420CDI, 2008, W211, V8, 180 000km

Wife's one: C-class 220CDI Sport Coupé, Euro, 2002, W203. 345 000km

Son's one: GLK class, 220CDI, 2009, W204

Sold: E-class 260E, 1988, W124, Wonderfull car sold after 489 000 kilometres of reliable services (engine M103, clutch, brake system and 5 speed manual gear box all original).

Sold: E-class, 320CDI, W210, 2000, 225 000km