I have a 2nd Gen Nest Learning Thermostat. We've had it for many years with no problems. Gas furnace, forced air. Yesterday I noticed that the house was 64 degrees (set to 68) and the thermostat was orange (calling for heat) but no heat was on. I turned it down, then back up, and it triggered the heat to start, but it only ran for a few minutes before turning off again. After doing this several times, it finally left the heat on long enough to get up to temp and worked fine the rest of the evening.
This morning, same problem. Set to 68, holding at 64 even though the thermostat was calling for heat. Turned it down, and back up, it turned the heat on for a few minutes then it turned off. I left it alone and it is basically cycling the heat for a few minutes at a time. I reset it, and still the same issue. Turns the heat on, then off a few minutes later, then back on, yada yada yada. There are no error messages displayed. We do not have a cooling system so it only affects heat, and we've made no changes to our furnace recently nor have we had an extreme weather event in Seattle.
Is the thermostat failing or is there something else we need to check or try? Of course, along the way, we got rid of our old thermostat after we'd had the Nest working well for a couple of years, so we don't easily have another to test the system with -- but if I need to find one I will. Just hoping for some advice on what might be wrong so I don't go too far down the wrong rabbit hole.
