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How to Clean a Pilot Light

The wonders of the modern world are simply amazing. And just as amazing is the fact that, as reliable as modern machine marvels are, a single tiny part can put a stop to everything. Your furnace is no different. You can have a few faulty parts and the furnace will still run fine, but there are a couple of pieces that will prevent your furnace from working if they’re broken, damaged, or even just dirty. The pilot light is one of those parts.

If the thermocouple is broken or covered in soot, it can prevent it from triggering the gas valve and starting the furnace. Of course, replacing a pilot light or thermocouple can be difficult, but if your furnace refuses to light because your pilot light is covered in soot and carbon residue, then it’s time for a quick cleaning.

You Will Need:

  • Pliers or Wrench
  • Wire Brush
  • Air Compressor (Optional but recommended)
  • Metal File
  • Old Towel


  1. Turn off the gas leading to your furnace. There should be a gas valve near your furnace, shut it off to stop the flow before commencing any work. Wait a few minutes (no less than five) to allow any leaked gas to dissipate first.
  2. Open up furnace cover and look at the pilot light and thermocouple. If they’re covered in black soot, grime, or a solid black mass, then it’s definitely time to clean them. Remove the bracket holding the thermocouple and pilot light and loosen the nuts holding the two in place using the pliers.
  3. Set both pieces on the towel (or some other soft surface which you can clean easily later.
  4. Use the wire brush to scrub the pilot light and thermocouple. Remove as much carbon buildup and soot from the tip of the pilot light as you can. Use the metal file for harder to reach areas and really dense buildup.
  5. Wipe both parts down with the towel to remove extra dust and replace the whole assembly back into the furnace.
Blue flames of a gas burner inside of a boiler

Flames should be almost entirely blue.

Once everything is connected, you can turn the gas back on and restore the furnace to operation. The pilot light should burn with a blue flame. If you’re using natural gas, the flame should be completely blue, with a white center. The only place where you should see yellow is at the tip of the white core, if at all. For propane, the flame should be almost completely blue. If anything more than the tip is yellow, you need to adjust your fuel feeds.

If your flame isn’t the right color, or your furnace still won’t light, then it’s time to call a professional as the problem is more complicated than a simple pilot light problem. You may have a bad thermocouple or a fuel-feed problem.


Cleaning the pilot light and thermocouple is part of regular furnace maintenance. Dirt and grime could be a problem if you didn’t have your furnace maintenance completed during the fall. After getting the system cleaned this year, be sure to have your full maintenance performed before the winter season starts next year!

Cassel Home Comfort Heating & Cooling is committed to being your best HVA/C contractor choice in Central Illinois in both Value and Customer Service! Call us to maintain your heating, ventilation, and air conditioning systems in the Champaign, IL area: (217) 866-1596.

A live call center and friendly technicians are standing by 24 hours a day, 7 days a week to help you with all your heating and cooling questions.