A furnace is crucial for maintaining a comfortable indoor space as temperatures drop. That said, you will likely encounter system issues with years of continued use. When this happens, you may notice several indicators of a malfunction. In most cases, these include a rumbling sound from the basement, clanking noise, or an air duct odor. Note that of all issues you are likely to face, an overheating gas or electric furnace poses a fire hazard in the event of obstructed airflow, mechanical failure, or simple aging.
It's never a good idea to do your own HVAC work. Furnaces have many moving parts and pieces which can break if not handled or assembled properly. There are also electrical and gas components that could lead to illness or injury if mishandled. With that being said, however, there are a few simple furnace "repair" tasks that are safe for a homeowner to handle on their own. If your furnace is not working, you may want to try these things before you resort to calling a furnace repair company.