I wasn’t sure by now, but today I tested and prove it! My air blower doesn’t work properly when I switch to take air from inside (recirculation). First time I thought I was too late when I switched and the outside bad smell already went inside. Second time I washed my car and I change the air knob to “recirculation” just before going inside to the car wash and the smell from chemicals got into the car in a minute. Today I played with the air system again and this is what I observed: I put the fan at maximum speed (4) and I tried to switch from outside to inside air combining with all other settings (up, down, +/- AC, etc). The air flow/sound did not change at all. On my other cars if I switch the air knob from “outside air” to “recirculation” I can definitely hear the sound of the air that’s taking now from the inside to the car. I went today to the car wash and again I felt the chemicals smell inside to the car. Weird, after playing another 30 min with the settings (engine idling) I could smell also something like coolant. It could be from AC. I’m curious if you guys can hear the difference when you adjust the air system to take the air from inside or outside. The sound it should be noticeable. Am I wrong?