I replaced the batteries in my thermostat after it displayed Lo Batt this morning. I am using 2 just purchased Duracell Coppertop AAA batteries. I threw the old batteries away and they have already been taken to the garbage. Now I am not getting any display at all on my thermostat. I replaced the batteries with the other two in the package and have pushed on the cover to be sure it is tight. The unit is only about 3 years old and was here when i bought the house. I do not know who installed it.