We bought a Honeywell Thermostat almost two years ago. It's worked beautifully until tonight. I noticed the thermostat was off, and I figured it was a dead battery. I replaced the battery, and it popped right back on if the switch is set to 'off' or 'cool'. If I flip it over to 'heat', the thermostat screen goes dead. What the heck is going on? Is this something we can fix? If not, is there a way to turn on the furnace without the thermostat hooked up? It's 5 degrees outside, the stores are closed and I'd rather not go the night without heat!

You never said what brand or model number you heat unit is but usually you can jump the R and W terminals together on the terminal strip located inside the furnace to bring the heat on. NOTE do not leave running in this condition if you are going to sleep.

Another possibility is the fuse blew that is on the circuit board in the furnace if so equipped. There are many other things that can cause your description also.