If you have an older gas furnace with a pilot light and it stops heating your home properly, one of the first things you should check is whether or not the pilot light is still lit. If the pilot light is out, then that's why your furnace is not heating—but you'll have to dig a little deeper to find out the cause of the dampened pilot light and what to do about it. Here are the basic steps you should follow.
Try relighting the pilot light.
Sometimes a draft may blow the pilot light out, or there may be a small air bubble in the gas supply, causing the flow of gas to be interrupted and the light to go out. If either of these issues are to blame, you can relight the pilot light yourself. Start by turning the gas supply to your furnace off so that if there is any gas accumulated near the pilot light, it has the opportunity to dissipate. Leave it off for 3 minutes before turning it back on. Then, use a long-handled lighter to introduce a flame to the pilot light. (You may need to consult your maintenance manual to find your furnace's pilot light). If the light ignites, you're all finished. If it does not, continue following this guide.
Check the gas supply.
It's possible that the gas has been turned off or disconnected. Call your gas company to ensure there have been no interruptions in service and that your gas has not been turned off for any other reason. If either of these situations are the case, having the gas reconnected will make it possible for you to relight the pilot light as instructed above.
Clean the thermocouple.
If your gas supply is connected and the pilot light still won't light, turn off the gas temporarily while you locate the thermocouple. This is the little apparatus that sits directly above the pilot light and detects whether or not it is lit. If it is dirty, it may "think" that the pilot light is not lit and turn off the flow of gas as a safety measure. You can clean the thermocouple by rubbing it with some sandpaper. Then, turn the gas back on and try lighting the pilot light again.
If none of these steps results in your pilot light relighting, then it is time to call a furnace repair company. Your thermocouple or pilot light apparatus may be damaged and in need of replacing. Click to find out more about furnace repair.