I had the same thing. I just fixed it today. I also searched various forums and websites to see how to fix it. And actually the tips work. If the LED on the button is on, the internal circuit is on, if it is off, the air is coming in from outside. In my case, whether the internal circuit was on or off, the flap was still flying. It was even so with the ignition on and the zero speed of the air supply. Some write about a decaying engine, others about the side clips holding the flap, and so it was in my case, or rather the broken left side of the upper part of the flap (such a white tube). I unscrewed the storage, then 3 screws (left side) holding the motor and the motor can be removed from the white handle, then the screws holding the housing with the blower - under the flap grille, then the screws holding the grille with the flap, then after moving the pit outside there is a grille mounted on the 4 star bolts, and under it in the middle one bolt holding the grill with the flap and from the inside you can remove the entire grill with the flap. After removing the grille with a flap, the flap is held on two such white handles on the sides. From the motor side, the strip into which the handle enters was cracked and therefore the flap was jumping. Gently with the forceps you have to pull out these white handles, turn the flap backwards to the front (180 degrees, as some write) insert the side handles and fold everything. It is a bit muddy, not enough space to unscrew the screws, but it was worth it, because it has been repaired and works, it hasn't been flying anymore, and I was ready to leave it permanently in the external circulation position and lock it.
