I have been using X10 systems for 15 years now, and they have all worked perfectly -- except this one. Every winter it stops working. Last year I went through all sorts of experiments trying to get it to work. I replaced it, and the replacement shows the same problem. The problems start around 40ºF. The unit is installed in the attic, which can easily get below freezing. The specifications state that it is good down to 0ºF but this is definitely not the case. I'm still not sure how to fix the problem.