My qestion is about my home heating furnace.
My home was built in 1991
The furnace is Gas and has the name Day & Night on the outside (not sure what brand that is)
I woke this morning to a very cold house. I listened for the heater and found it was coming on for about 30 seconds and then off for about 2 minutes. I just kept doing this all night and morning. I replaced the thermostat about 2 years ago with a honeywell brand digital display but very basic model and it has worked fine. It has kept the tempature at exactly what I set it for until this morning. Any idea why it would cycle so quickly and not keep the home at the tempature that I set it for? Temp set at 72 degrees and was 66 in the house this morning.

Randy

I can think of 2 reasons. Both have happened to me. It can either be a bad hot surface ignitor (which frequently go bad and can be changed out if you have the right part) or a bad flame sensor. If there is a flame and then it shuts off, that is a flame sensor problem and can be fixed by simply cleaning the flame sensor with sandpaper. If the furnace tries to start but no flame comes on, then check the hot surface ignitor.