When I have mine on auto it pulls in fresh air all the time. I only put it on max when I pull up next to a stinky car or someone is smoking next to my car. When I put it on max you will hear a door close, causing the air to recirculate. The fan speed sometimes goes up a little, but not always. The air temperatur sensor should be around the climate controls just like on the Gen 4's. On top of the dash is the light sensor, but I could be wrong on the Gen 3's though.