First blizzard warning in Wisconsin for over 10 years and our furnace decided to stop working this morning. At least I was home because of the weather. Still had to drive a hr round trip in the snow and hope the after market sensor works. It is, for now…
Nice job! I had a fun one 2 winters ago, the glue on the pressure sensor switch just failed, I’ve never heard of this happening before. (Admittedly I’m not reading stuff about gas furnaces daily, but still…) The black piece and the white piece separated in the pic.
So the gas turns on, and the fan starts speeding up and there’s a pressure switch I guess to make sure there’s gas flowing, and the fan is blowing before igniting and starting the whole reaction, and since the switch wasn’t working, it wouldn’t ignite.
I tried to re glue the 2 plastic halves back together but the glue wasn’t holding, so I just zip tied the hell out of the thing, and its been working great for 2 years so far…
Just as a clarifying point(I’m sure some HVAC person can correct me). The fan spins up to make a draft, the pressure sensor is detecting negative pressure(vacuum) and that successful check allows the gas valve to open prior to the igniter/flame sensor. The draft helps pull the gas into the combustion chamber and not just leak it out into the basement or wherever(especially if it fails to ignite). Furnaces kicking on are a series of do an action, verify that action happened, repeat until it gets through its todo list. High efficiency furnaces work similarly but also different…
Knowing the general boot up can help figure out what isn’t working. Igniter never goes off?…pressure sensor is right before it. Furnace ignites but shuts off a few seconds later…Flame sensor didn’t report success.
I keep a pressure sensor, igniter, and flame sensor sitting next to my furnace. It’s like ~$50 for the OEM parts and I can generally fix my furnace in 5-10 minutes.