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Pulse G14 Furnace Sputtering and short cycle (8-12 secs)

I have G14q3-80-2. Has ran flawlessly for years. This season started to sputter. And short cycle. I serviced the purge/ inducer pump, airflapper, cleaned the fiberglass disc and plates, refitted. Also took cap off exhaust, got about 5 ounces of crud from there, rust wet muck.... Replaced front plate. Same issue. Here is the link to youtube I made a short video.

Took off front plate and did a test restart: as it seems like its either starving for air or cant get exhaust out. Fired it back up without the plate on, to test intake air flow. Same issue. Like it has the hiccups lol. And short cycles. Any advice??


  • ratioratio Posts: 1,813Member
    There are very few pulse furnaces still in operation around here. It might be time to budget for something a little newer...
  • Steve MinnichSteve Minnich Posts: 2,192Member
    Plugged condensate drain?
    Steve Minnich
  • DZoroDZoro Posts: 669Member
    Pretty much time for a upgrade, would be surprised if it would pass its annual pressure safety test that should be done.
    Did you clean the flapper or install a new one?
    Is the exhaust pipe inside nice and white?
    Inside the bottom of the condensate trap tube there is a 1/2" tube that almost goes to the bottom try to get a wire up inside that tube to clean it. Just make sure you replace the bottom cap and it is sealed properly when done.
    The new furnaces are so much quieter ;).
  • HandiguyHandiguy Posts: 4Member
    Cleaned the flapper, didnt appear to show signs of damage.
  • HandiguyHandiguy Posts: 4Member
    Upon ignition has normal force of exhaust pressure and then a vacuum burst cycles then back to exhaust. Thanks D ill check the 1/2 in drain tube.
  • SuperTechSuperTech Posts: 667Member
    It sounds like you have a condensate drainage issue. You need to try clean it out. I bet if you cut open the PVC on the bottom left side of the furnace that it's plugged with muck. You can use a fernco coupler to put it back together.

    Those furnaces are known for heat exchanger failure. I've condemned many that didn't pass a pressure test. You should budget for replacement even if my idea works.
  • DZoroDZoro Posts: 669Member
    Put in new flapper, have never had a good success rate cleaning the flapper.
  • HandiguyHandiguy Posts: 4Member
    Love the concept of the system. Noise is okay. I believe they were ahead of the times...
  • Steve MinnichSteve Minnich Posts: 2,192Member
    @Handiguy - I beg to differ. I cut my teeth on those in '81 and '82 and there were so many issues. Carrier had the 58SS (?) 90+ out at the same time and it was a piece of cake installing with minimal service related problems. I think Lennox over-thought this one.
    Steve Minnich
  • Steve MinnichSteve Minnich Posts: 2,192Member
    It may have been the SX?
    Steve Minnich
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