Why Your Furnace Pilot Light Keeps Going Out and How to Fix It

A furnace pilot light that keeps going out is a common issue for many homeowners, especially during colder months. This problem can disrupt heating, cause discomfort, and even lead to larger appliance failures if left unattended. Understanding the reasons behind a repeatedly extinguishing pilot light and the appropriate steps to fix it can save time and money. Below is a detailed guide to diagnose and remedy this issue safely and effectively.

Common Causes	Symptoms	Recommended Actions
Dirty or Clogged Pilot Orifice	Pilot light flickers or won’t stay lit	Clean the pilot assembly or replace clogged parts
Thermocouple Malfunction	Gas valve shuts off, pilot light extinguishes	Test and replace faulty thermocouple
Drafts or Airflow Issues	Pilot light blows out frequently	Seal drafts; adjust airflow near furnace
Gas Supply Interruptions	Weak or no flame on pilot light	Check gas valve and supply line for issues

Understanding the Role of the Pilot Light in Furnaces

The pilot light is a small, continuously burning flame that ignites the main burners in a gas furnace. It provides the necessary ignition source to start heating when the thermostat signals the furnace to operate. Without a stable pilot light, the furnace will not heat properly. Maintaining a steady pilot light is critical for efficient furnace operation and safety.

Common Reasons Your Furnace Pilot Light Keeps Going Out

Dirty or Clogged Pilot Orifice

Over time, dust, dirt, and debris can accumulate in the pilot orifice, the tiny opening controlling gas flow to the pilot light. This buildup restricts gas, resulting in a weak or flickering flame that easily extinguishes. Regular cleaning of the pilot orifice prevents clogging and maintains a strong pilot flame.

Faulty Thermocouple

The thermocouple is a safety device that senses if the pilot light is lit. When it heats up, it signals the gas valve to stay open. A malfunctioning thermocouple can incorrectly detect the flame is out and shut off the gas supply, causing the pilot light to go out repeatedly. Testing and replacing a defective thermocouple is often necessary for a reliable pilot flame.

Drafts or Poor Airflow Around the Furnace

Drafts from open windows, vents, or gaps near the furnace can blow out the pilot flame. Similarly, excessive airflow from fans or air ducts can destabilize the flame. Eliminating drafts and improving furnace area airflow stabilizes the pilot light.

Gas Supply Problems

A weak or interrupted gas supply is another reason the pilot light may not stay lit. Issues such as a closed gas valve, low gas pressure, or kinks in supply lines reduce gas flow. Ensuring a consistent and adequate gas supply is vital for a steady pilot light.

Step-by-Step Guide to Fix a Furnace Pilot Light That Keeps Going Out

Safety First

• Turn off the gas supply before inspecting or repairing.
• Ventilate the area to avoid gas accumulation.
• Use protective gloves and eyewear if necessary.
• If unsure or uncomfortable with gas appliances, contact a professional technician.

Inspect and Clean the Pilot Orifice

• Locate the pilot assembly near the burners.
• Use compressed air or a soft brush to remove dust and debris from the orifice.
• Check for soot buildup and clean with a needle if needed.
• Re-light the pilot to check if it stays lit consistently.

Test and Replace the Thermocouple

• Turn off gas and remove the thermocouple for inspection.
• Look for signs of wear, corrosion, or damage.
• Use a multimeter to test its voltage output when heated.
• Replace the thermocouple if it’s faulty or damaged.

Check for Drafts and Airflow Issues

• Inspect the furnace area for open windows, vents, or holes causing drafts.
• Seal any gaps or openings with weather stripping or caulk.
• Adjust vents or fans that might be directing strong airflow near the pilot light.

Verify Gas Supply and Pressure

• Confirm the gas valve is fully open.
• Inspect the gas line for bends, damage, or leaks.
• Contact the gas utility company if low pressure is suspected.

Preventative Maintenance Tips to Avoid Pilot Light Issues

• Schedule annual furnace inspections and tune-ups.
• Keep the furnace and surrounding area clean and free of dust.
• Ensure proper ventilation in the utility room.
• Regularly check for drafts throughout colder months.
• Replace the thermocouple every few years as recommended.

When to Call a Professional HVAC Technician

If the pilot light continues to go out despite cleaning, repairing, and checking the system, it may indicate more complex issues. Problems such as malfunctioning gas valves, blocked vents, faulty control boards, or deep mechanical faults require expert diagnosis. Professional technicians have the expertise and equipment to safely address these problems and ensure your furnace operates reliably and safely.