Furnace control board still had power and three amp fuse was not popped. Thermostat did not have batteries inside it as a back of power so we put batteries in and thermostat turned on and ran furnace as it should. After talking with customer, they will decide if they want to replace the thermostat or not. I told them if they would like to replace it then to just give us a call and we can get someone out to do that.