My furnace is 17 years old and it's starting to give me problems. I've had my furnace stop working about once a year for the past few years, but thankfully every issue I've had has been quite simple to fix, mostly because I know a few basic troubleshooting steps.
I was going to write a blog post describing some of these troubleshooting steps for furnaces, but I decided that a video might be a little easier to follow along with. This video is by no means a complete troubleshooting guide to furnaces, but it's a nice introduction to furnace troubleshooting. I cover the most basic things to check, and I discuss some common error codes that furnaces may give. For detailed troubleshooting and repair steps for furnaces, check out http://www.grayfurnaceman.com/ . This is the best web site I've found that deals with furnace troubleshooting and repairs.
I'm no heating contractor so I don't know the exact numbers, but I'd guess that a large percentage of "no heat" service calls could be addressed by homeowners if they just knew where to start. That's what this video is all about. Oh, and while watching the video, please ignore the part where the camera goes out of focus. I don't know why that happened, but you're not missing anything. Without further ado, here's the video:
I still recommend annual furnace inspections though.