How To Light a Natural Gas Furnace

Natural gas furnaces have either a pilot light or an electronic ignition. Older ones are the pilot type that you can reignite, while the newer ones are furnaces with electrical set-up to ignite the gas. Electrical systems are tricky so that, in case you have one of those, you will have to call a qualified repair person to reignite your furnace. Never try to fix this problem yourself.

For a natural gas furnace that makes use of a pilot light, it would be easier to re-light it and you can do it yourself. Here’s how.

  • Turn off the gas source. First thing that you should do is to turn off the gas source by switching the dial. Wait for 10 minutes for the gas to clear before. Make sure that the area does not have any gas fumes after this time. If it still does, contact a qualified repair person to check for possible leaks.
  • Remove the front access cover. Do this only if the furnace is free of gas fumes. Removing the cover will reveal a switch with the options ON, OFF, and PILOT.
  • Move the switch to PILOT. Carefully turn the dial from ON to the PILOT setting. Push the button until you hear a clicking sound. Hold the button for 60 seconds to keep the gas flow. A blue flame will appear.
  • If after 60 seconds of holding the button no flame is seen, light the furnace with a match or a lighter. Release your hold on the gas button and let the fume clear again for a couple of minutes before proceeding. Then, light the furnace with a match or lighter. It is advisable to use an extended tip lighter or a long-stemmed match for this step to avoid any accident. Place the flame above the pilot light gas inlet tube. Hold the button while doing so and keep holding it for 60 seconds. Then, release the button and turn the dial from PILOT to ON.
  • If it still would not light, check for possible damages. The most common reason why the furnace would not light is the thermocouple and fuse. Try to reach the thermocouple and use a wire brush and dry cloth to clean it. The thermocouple is found at the tip of the pilot light. After cleaning the thermocouple, repeat the steps above on relighting. If it still does not light, you will have to replace the thermocouple.
  • Return the front access cover. Make sure it is securely placed back. Set your preferred thermostat.

Call an experienced repair person if the pilot light still does not stay on after you've cleaned and replaced the thermocouple. If you have a furnace handbook, read it carefully before attempting to light it. Check if your other appliances that run on gas are working. It may be that the gas supply in your house does not work; hence, the light would not stay on the furnace.

If you smell gas and it will not go away, leave the house immediately and call the fire department or Gas Company to check for leaks.


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