Being the dummy that I am I should have known but I tried it anyway. I have a gas-forced hot air furnace with the old type mercury thermostat. We decided to get modern and install a digital thermostat. The old one is a two wire (red & white) unit so when we bought the new one we got the same type. It is my understanding that the red wire provides power for the read out, but as luck would have it we are getting no read out and the furnace will not come on. I put the old one back and the system works fine. Did I do something wrong, is the thermostat bad .......??? Any help, suggestions and ideas are appreciated.