Thanks for that good description and the suggestions on how to avoid the noise. Indeed the noise I hear is the servo moving the door back and forth -- often as fast as once a second. I had discovered the fact the MAX COOL will lock the door to one side, but I'm not sure that I can attain good temperature control by just using the fan speed setting when it's in that mode -- I'll try it. I'm surprised that the mileage would improve in MAX COOL mode as the AC compressor would be on all the time, right?