I have 2 Honeywell T8001 thermostats - on the downstairs the display goes blank and then comes back on randomly. I have took the downstairs thermostat and installed it upstairs and it works fine. When I put the upstairs thermostat downstairs, it goes blank and comes on randomly.
There are no batteries in the thermostat. This is been going on for about 2 weeks. Any idea where the problem could lie? Thanks for any suggestions.

Check for a common wire connection( "C" terminal ) at the thermostat and furnace, make sure they are not loose. Usually if they don't have a common wire they will go blank and then will come back on by themselves. Good luck, Mike

Mike (Acetc) - thank you for your response. I found the problem - The problem was the switch -the wire from the breaker box connected to the switch before it goes to the Furnace (Blower) - the switch was broke (it seems like it may have been broke since it was installed. With this extreme heat were experiencing in Atlanta, GA it would make contacts and disconnect throughout the day. I hope this answers helps someone else. Pete