That is the blower switch & there is a cable that attaches to it that controls the fresh air door under the passenger side of the dash. MOST of the time that cable siezes up & then damages the blower control switch.
You could try disconnecting the cable first.
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)