Sometimes, you try to pat yourself on the back, and you end up dislocating your shoulder.
I probably should not have posted the list of things I've accomplished around the house, because it must have awoken the angry housing gods. Less than 36 hours after my post, I got up to get dressed in the morning, and noticed cold air blowing out of my heat vent. With a sinking feeling, I checked the thermostat and confirmed that it was only 64 degrees in the house—definitely not warm enough for the furnace to be on its cool-down cycle already.
I stayed calm! I troubleshot my furnace like a pro, and this is what I concluded:
- It was blowing cold air even though it was not warm enough in the house
- The burners inside the furnace were not burning
- It would not turn off, even when I set the thermostat to OFF.
I consulted the internet about this somewhat bizarre behavior, and I determined that there were 2 likely causes.
- The furnace could have overheated due to a clogged filter
- The thermostat could be sending faulty signals to the heater, which is likely in the case of low batteries
Well, the first condition was easy enough to test. I took out the filter and examined it—clean as a whistle! The second test took me a while. Since my thermostat wasn't flashing a low battery signal, I disregarded the batteries and just assumed that if anything was broken, it was the thermostat itself, seeing as it looked like it had a few years under its belt. Fortunately, I have a backup thermostat (the one I bought for the apartment), so I took all the wires and batteries out of the existing thermostat and put them in the new one. The new thermostat kept flickering and beeping and wouldn't do anything right, so finally I conceded that maybe the batteries were the problem. I installed new batteries, and the thermostat behaved normally, so I re-hooked up the old thermostat, using the new batteries this time. This resulted in no change—the furnace kept blowing cold air incessantly. After messing around with the thermostats for a while, I was reasonably certain that they were working as they should, because I was hearing the appropriate "clicks" when they were cycling on and off.
Given that the furnace is "probably as old as you are," (as a technician said to me once) and that I'd been advised to replace it by every single qualified person who ever looked at it, I was pretty sure that the furnace had finally lost its mind and was in need of professional help. I was also hoping that there was something so wrong with it that my home warranty would finally cover its replacement, which was the whole reason that I'd been given the home warranty in the first place.
Apparently the housing gods aren't completely irate with me, because they did wait until a 60+ degree day to knock my furnace out of commission, and the warranty company was able to get me an appointment to have it looked at the very same day.
The tech who visited used a lot of words that I immediately forgot, but the gist of it was: flames are blowing out of my furnace in the wrong direction, causing parts of it to overheat, and triggering a safety switch to turn off the flames and blow cold air to cool itself down. The reason the flames are misbehaving is likely a crack or leak somewhere.
The takeaway from this story is the following: If your heater is blowing cold air, the burners might not be working, and if your heater won't turn off, the thermostat might not be working. But if your heater is blowing cold air AND won't turn off, it's probably because it's been overheating, and there are more reasons for overheating than simple clogged filter.
Sadly, though, this is not something that can be done immediately. First, the repair company needs to check with the warranty company to find out if the replacement will be covered. Then, they'll need to order the new unit and perform various feats of bureaucracy, and I probably can't expect to have a fully functioning heater for a week or more. While I'm waiting, I expect to be very cold.
Rest assured this will be a story in installments. Keep your eyes open for follow-up posts, and in the meantime, keep the home fires burning! Or not, as the case may be.