Your furnace is outfitted with either an electronic ignition or a pilot light. Your furnace relies on these components to ignite the burners when the gas clicks on for a heating cycle. If you can’t tell whether or not you have a pilot light or an electronic ignition, you should be able to either see the pilot light (which will be a small blue flame), or hear the ignition clicking on when your furnace begins to heat. Both of these components can fail, and your thermocoupler (which is a failsafe that closes off the gas source to your pilot light) can also fail — which means that your furnace won’t be able to heat up. If you have a pilot light that is out, you may be able to reignite it, following the instructions in the next section.