How to troubleshoot a furnace pilot light that won't stay lit

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Things You'll Need

  • Old toothbrush

  • Water displacement spray

  • Compressed air

  • Clean cloth

  • Pliers

  • Screwdriver (if necessary)

Furnaces of various kinds are gas powered and use a pilot light to supply heat to the unit, including standard home furnaces and floor furnaces. This pilot light may not always stay lit, due to a variety of issues that may affect the gas supply or ignitor. Troubleshooting this issue may be helpful in determining the source of the problem and helping users identify a potential resolution. Maintenance or troubleshooting should only be performed by adults familiar with operating large gas appliances.


Step 1

Turn off the furnace, unplug from the power supply, and turn off the gas supply. Wait five minutes to allow gas to exit the lines before performing any cleaning or maintenance on the unit.

Step 2

Locate the pilot burner and clean with an old toothbrush lightly sprayed with water-displacing spray, commonly available at most hardware stores or home repair stores. One brand name is WD-40. Wipe the burner clean with a dry cloth.

Step 3

Clean any debris from the air hole on the burner, which will prevent proper air flow and result in an unstable pilot light.


Step 4

Blow some compressed air through the flame orifice and air intake. Cans of compressed air can be purchased at most hardware or home repair stores.

Step 5

Examine the area for strong drafts from doors and windows that may be negatively affecting the pilot light. Block the drafts if possible.

Step 6

Tighten the thermocouple, which is the metal bracket that surrounds the pilot light.

Step 7

Contact an authorized service technician if the above steps do not resolve the issue.



Meredith Jameson

Meredith Jameson writes early childhood parenting and family health articles for various online publications. She holds a Bachelor of Arts in history from San Francisco State University.