I had a Honeywell digital thermostat in a good interior wall location. It
seemed to behave well except when it was really cold outside. When that
happened, my setting of 68 would invariably go to 72, and sometime more.
Thinking that the thermostat was defective, I bought a new one and it still
continues. Can anyone advise why the thermostat won't cut out the furnace
when the setting temperature has been reached ... only when it's extremely
cold outside?