We are closing in on the 150" mark for snow this year, and I finally have found the difference between the AT9 and the AU9. The reflector is very sensitive to snow buildup. My AU9 is at the same location as the AT9 (which never had an outage in two years) and this year the AU9 has kept me busy brushing off the snow........makes a person almost ready to join "masterdeals" down in the banana belt 
