I have a new, 3-year old, high-efficiency, gas furnace in my home. I recently realized that my draft inducer, which normally kicks on before the burners and before the main blower, is not stopping.

In the past, this was the normal sequence: 0) Everything Off; 1) Draft Inducer starts; 2) Burners ignite; 3) Blower starts; 4) Burners cut out; 5) Blower and Draft Inducer stop.

Now, instead of the blower and draft inducer both stopping, the blower alone stops. The draft inducer continues to run. The Burners kick on, etc. Instead of 1-5, it's going 2-5 without the draft inducer ever stopping. Why? What should I do about it?

Maybe I'm asking the wrong question. Maybe I ought to be asking why my furnace isn't staying on long enough to raise the temperature 3 degrees. I think it's shutting off prematurely and immediately starting a new cycle.

  • I think it may be my thermostat failing. This morning, after waking and turning up the thermostat setting to 67, the furnace went through three cycles--of course, with the draft inducer never seeming to turn off. So, I went to the thermostat. It read a room temp of 68, meaning that it should have been waiting for the room to drop temp before kicking on the thermostat. I dropped the setting to 66. The inducer stopped. The room temp returned to the screen as 70.
    – David
    Jan 16, 2013 at 13:49
  • What is the make and model of the furnace and thermostat? A thermostat is typically an over elaborate temperature switch, and usually doesn't have much to do with the furnaces operation other than telling it when to turn on. I would be more focused on the furnaces control board, since that's typically the brains of the operation.
    – Tester101
    Jan 16, 2013 at 14:11
  • The comment about the thermostat makes me wonder if the lower stage of a two stage furnace isn't working.
    – BMitch
    Jan 16, 2013 at 14:17
  • It's a Comfortmaker C9MPD100J14C. The thermostat is a Honeywell RTH230B.
    – David
    Jan 16, 2013 at 18:26
  • You might check to make sure the furnace is not overheating. Overheating will cause the symptoms you described. Once the burners shut off the furnace cools down and then starts again. This can be caused by ducts that are too small, a furnace that is too large or even a dirty filter or combination of all 3.
    – user76730
    Apr 25, 2018 at 16:12


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