I attempted today to switch out my current thermostat with the HAI Omnistat2 RC-1000. I have a single stage system with heat and cool. I wired it matching up the wires to the appropriate terminals (I checked it 3 times). During testing, I can get the fan to come on with the thermostat, but when I switch it to cool, the air does not come on and the thermostat "clicks" every 10 or 20 seconds. It seems as though it is trying to turn the air on, but it can't. My furnace (and house) is two years old. I did not think I needed the power supply (HAI 30A00-2), but maybe I do. My current thermostat uses batteries that I thought were to keep the settings, but maybe the batteries help power on the system. Anyway, I wanted to check here before I call someone as this may be a simple issue that others have had as well.