I had similar issues in Chicago. My high-efficiency furnace had issues in 2019 when we had -30f weather for a few days. Basically it's a multistage condensing f

I had similar issues in Chicago. My high-efficiency furnace had issues in 2019 when we had -30f weather for a few days. Basically it's a multistage condensing furnace, and on those really cold nights it would fail to kick into the later stages. After failing so many times, it would enter a "reset" mode, where it basically would shut down for 10+ minutes at a time, which isn't great when it's really cold! In trying to fix it, I had multiple techs come out and none really fixed the issue. These are basically some notes on the experience: - First tech stayed for 6 hours. Cleaned the system, replaced a high pressure switched, and readjusted the PVC in and out takes. The pressure switch alone costed over $500 dollars. He did the PVC for free. The problem persisted after he left. - First tech sent a second guy out the next day. This guy comes in and within 10 minutes recommended replacing my Nest with their "preferred" smart thermostat for a cost of $500. He also wanted to redo my humidifiers water setup ($200), and redo the elbow joint in the condensation output of the furnace ($200). After he quoted me all of that I asked him to leave. I redid the condensation output myself ($15 in parts), and humidifier ($15 in parts). I looked up the high pressure switched they replaced, and was shocked to learn it only costs $150. - I wrote my first Yelp review ever because of this company. They contacted me a day after I posted my review asking me to take it down in exchange for a partial ($300) refund. I agreed. - I had two family friends who do HVAC come out afterwards to look at it. After seeing that it was a high efficiency unit they basically wouldn't touch it. They are older and basically said they never retrained for high-efficiency units. It was never needed because they have more work then they can handle with older units. All they were able to offer was to give me a good deal on replacing it with a less efficient unit if I wanted. At the end of the day my issue was never fixed. Luckily we haven't had as cold of weather as that week, so the issue hasn't manifested again. If it happens again I honestly will cross my fingers and hope the next company that I use is more helpful then the previous.