Furnace runs when I turn swiitch on or turn thermostat down then up. Once it gets to temp required, it does not kick back on, unless I do the aformentioned turning it off and on again. For two nights it worked for five or six hours-then during the day its not kicking on again when it gets cooler, until I kick it on and off again. Propane gas. Help (mercury type thermostat) Help!

