Mercedes Climate control fan & Temp sensor.  This is the device that the climate control uses to determine the interior temperature of the car.  If defective, generally the climate control will still work, but only on full high or full low.  Fits many older mercedes models.  See your original part number, unit mounted on the dash board.  240D 300D 300TD 280SE 280SEL 280E 380SE 380SEL 500SE 500SEL 300SD 300SDL and more!