I have a Lennox G26. I have noticed lately being home all day for the holidays, The furnace seems to cycles on and off, about every 3-4 minutes, sometimes longer, sometimes shorter. (burner and blower motor), a few times before changing the system "on"status on the thermostat back to off. It also comes back on a and does the same thing about 10 15 minutes later. Temp on the thermostat still shows the set temp. I would only expect the furnace to start again once the temp dropped 1 or 2 degrees.