[kwlug-disc] winter and furnace

[Tim Laurence]

Perhaps a coincidence but something similar happened a couple weeks ago at my place. The induction fan was ramping up to a very high speed (we could hear while upstairs). It was ramping up through speeds trying to confirm it could push a draft through the flue.

The error code indicated a pressure switch was malfunctioning. With some research I found out this was common failure. One of the posters mentioned they hit the pressure switch with the handle of a screwdriver to unstick it. I did that and it worked like a charm but I also ordered a replacement which I installed last week. I wonder if the issue was just some gunk (maybe ice) I knocked loose.

--
Tim Laurence

On February 9, 2026 at 1:24:42 PM, Mikalai Birukou via kwlug-disc (kwlug-disc at kwlug.org (mailto:kwlug-disc at kwlug.org)) wrote:

> There are these little pipes that go between enclosed area in furnace
> and membrane switches to detect presence of pressure difference between
> normal/room and that enclosed area with air/fumes flow.
>
> Other season, there was a burned ash in one of pipes, after burner, I
> suppose.
>
> One more season, I gently blew in and out of pipe into membrane switch
> to hear it flip. It got unstuck, and continued proper operation.
>
> This season, a pipe had a drop of water in it. Surface tension in a
> small radius obvious stopped pressure difference from pushing membrane.
>
> I guess, cleanup includes dusting furnace, and blowing through some
> pipes. :) Noting that three events happened over 15 years.
>
>
>
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