Save money by diagnosing furnace problems yourself

tl;dr I saved a bunch of money by diagnosing furnace problems myself, instead of calling in a technician.

Two weekends ago the furnace was on the fritz. It clicked on to start running and my girlfriend smelled gas. That was at 10pm. We switched off the furnace, called the gas company to send out a technician, and waited. He arrived after midnight, which gave us plenty of time to worry about all the things that could be wrong, how much money it would cost to replace everything, and of course, what it would be like for our house to blow up.

The technician was a nice guy. He assured me in no uncertain terms that our house was not about to blow up. He popped open the furnace case and took a look. It seemed the hot surface igniter was heating up, the gas was kicking on, but the gas wasn't igniting before an automatic fail-safe shut down the process (to prevent gas leaks). At the time he said our igniter was probably bad, that we should call a HVAC technician in the morning and not worry too much. (Spoiler alert: it wasn't the igniter, which makes sense since the igniter was heating up just fine).

Naturally I figured it was the igniter, since that's what the gas technician said. I also figured I should leave this matter to the professionals. The gas technician shut off the gas line to the furnace, wrote up some scary looking OPEN AT YOUR OWN RISK-type warnings and put them in appropriate places on the furnace — typical cover-your-butt stuff. So I called up the company that I already used to inspect our air conditioning unit. I fully expected to set up an appointment and do whatever they recommended.

But then we got into the details. I mentioned to the receptionist that the gas technician said it was probably our hot surface igniter. Is that usually an easy fix? "It depends. We might not even stock your igniter. What's the model of your furnace?" I read her some names and numbers that looked relevant. "It doesn't look like we have those parts in stock. I'll have to get in touch with a technician to see if he has a universal igniter that will fit." Alright, fair enough. How much will this cost? "$90 for the service call. After that it's parts and labor." Can you give me a ballpark on how much that might be? "Sorry, the technicians handle that." Really? You can't give me any sort of estimate? "Sorry." Alright, thank you. I'll call you back to schedule something.

At this point, I'm worried. I'm worried about opening myself up to a big financial risk, on the order of hundreds of dollars, for what might be a wild goose chase and replacing the whole furnace anyway. I'm worried about being over-charged on an easy repair, or a part I can get for half the cost online. I decide it's worth looking into myself first. I can always call in the professionals later.

First I crack open my furnace, warning labels be damned. I turn the gas on and have it run again. Same thing, igniter heats up, gas kicks on, gas doesn't ignite, gas kicks off. Okay cool. I'm still operating under the assumption that the igniter is bad, maybe it's not getting hot enough or something. I figure out how to unscrew it and pop it out. Now I start googling around for where to buy this part. Is there some local HVAC supply store I can go to? It's the weekend, and they're all closed. Maybe I can get it shipped quickly? Here's one, same model number, but it won't get here until Tuesday. Okay, that's an option.

There I was, all ready to buy a replacement part. But it would take days to arrive, and I wasn't even sure that would fix my problem. So I kept researching. Youtube is fantastic for DIY home repair how-tos. I found a couple of guys taking apart their furnaces, explaining what each part is, how the ignition system is supposed to work. That's when I learned that when hot surface igniters fail, they fail by cracking or breaking so they don't heat up at all. Hmm, very interesting, because mine was still glowing just fine. I didn't have an ohm meter to test whether or not it was broken for sure, but "the igniter is fine" was my new operating assumption and I made a note that probably I should own a multi-meter for answering such questions about when electrical devices are burnt out.

With fresh resolve, I kept googling until I found a website for troubleshooting all the things that could possibly be wrong with your furnace. I found a scenario for all the symptoms I was seeing: igniter heats up, gas kicks on, but gas doesn't ignite. The website said that the gas nozzle might not be positioned properly, so it's not blowing over the igniter — that or something is wrong with the flame detector.

I re-installed the igniter, this time shifting it back or forth just a little bit from where it was positioned earlier. And what do you know, after a little fiddling, the gas ignited properly.

It was all pretty awesome. I solved a problem myself, learned a lot about my furnace in the process, and saved at least a hundred dollars. To celebrate, I invested some of the money I saved into tools for future money-saving endeavors: a multi-meter, a kill-a-watt, and a package of incense sticks (for checking for drafts). Total cost: $46.72 through Amazon.com. Previously I had bought some rope caulk to seal up my windows, and the next day I decided to take the plunge and buy a clothes drying rack — but those are stories for another time.

In conclusion, furnaces are not as scary as I thought before. Once the guy from your gas company tells you that the house is not going to blow up, you can learn a lot (and potentially save a lot of money) by looking around in there yourself.