Does anyone know exactly where the air quality sensor is located at the FL ? In the TIS the air quality sensor P84 is in, also that the plug in the wire harness is moved to the right end wall side, but the installation location is unfortunately not defined. So far I was mistakenly the assumption that it is the sensor above the pollen filter in the blower box, but because I was only recently allowed to deal with the heater in detail thanks to the defective one, I found out that it is at the front of the fan The reason for the question is : My ECC works until now inconspicuously (*three times knocking on wood*), the manual convection air circuit works the same way, the flap closes and opens audible. But… the automatic recirculation air (symbol : three arrows in the circle with the “A” in the middle) cannot be activated. As far as I know, the automatic recirculation air is activated by pressing the button twice a second time. . that just doesn’t work, no matter how fast one presses one after the other, it ends in switching on and off the circulating air. How do I get out why that doesn’t work ? I can’t even find an approach via the OBD adapter including OP-COM ! Thought it could be due to a not properly functioning air quality sensor ?! Who has an idea ?? Thanks in advance