Rheem RGTK09EZAJS Gas Furnace. Blower fan has turned on in middle of night even though T Stat set to "Auto". The first time I woke up to fan running non-stop and the "Cool/Off/Heat" on T Stat was set to "Off". The next two times it did same thing with T Stat in "Heat" position.
Heating cycle worked normal a couple of times each morning and the Blower turned off appx. 2 minutes after burners shot off. Only have had furnace on a few times in AM since afternoon is not needed yet due to mild temps outside.
Any ideas why this happens or what things to check first? This model has a Circuit Board control and is a 2006 model year.
Thanks for any help.