Why Did the Pilot Light on My Gas Furnace Go Out?

If your gas furnace in West Milford suddenly stops working, a pilot light that’s gone out is often the culprit — especially in older furnaces with standing pilot lights. While many newer models use electronic ignition, thousands of homes still rely on traditional pilot lights to keep their furnaces running.

A pilot light can go out for several reasons, ranging from something as simple as a draft to issues that require professional attention. Below, the West Milford heating pros at Mark Lindsay and Son Plumbing & Heating explain the most common causes, troubleshooting steps, and when to call a pro (ie: us!).

Common Reasons a Furnace Pilot Light Goes Out

1) Weak or Unstable Flame

A properly functioning pilot light should burn steady and bright blue. If it appears yellow or flickering, it can indicate:

• A gas leak or improper gas-to-air ratio
• A dirty burner
• Insufficient gas pressure

When this happens, most furnaces automatically shut off the gas valve as a safety measure, which extinguishes the pilot light. If your flame is yellow, turn off the furnace and contact a licensed technician immediately — this can indicate a potentially dangerous leak!

2) Dirt and Debris Buildup

Over time, dust and debris can clog the intake valve or pilot orifice, making it difficult for the flame to breathe. This reduces the flame’s strength and may cause it to go out completely.

Routine maintenance, such as annual furnace cleanings, helps prevent buildup. If you suspect a blockage, avoid poking around the pilot assembly yourself — this is best handled by an HVAC professional.

3) Damaged or Malfunctioning Thermocouple

The thermocouple is a small but critical safety device that senses the pilot light’s heat. If it detects that the flame is out, it cuts off the gas supply to prevent leaks.

When a thermocouple is dirty, misaligned, or damaged, it may incorrectly sense that the flame is off, even when it’s not — shutting down the gas valve and extinguishing the pilot light. A faulty thermocouple often requires cleaning, realignment, or replacement by a professional technician.

4) Drafts or Airflow Issues

A strong draft is one of the most common — and easiest-to-fix — reasons a pilot light goes out. Drafts can blow out the flame through:

• Open basement windows
• Gaps near the furnace
• Poorly sealed utility rooms

Check for obvious airflow issues around your furnace. Once resolved, follow your manufacturer’s instructions to relight the pilot light. If the flame won’t stay lit after several attempts, call us at Mark Lindsay and Son.

Troubleshooting a Pilot Light That Won’t Stay Lit

If your pilot light keeps going out, follow these general troubleshooting steps (always consult your manufacturer’s manual for specific instructions):

1. Turn off the furnace and wait at least 5 minutes to allow any gas to dissipate.
2. Locate the pilot light assembly and the reset or ignition button.
3. Turn the gas control knob to “Pilot.”
4. Hold down the reset button while using a long lighter to relight the pilot.
5. Continue holding the button for 30–60 seconds after the flame ignites.
6. Release the button. If the flame stays lit, turn the knob to “On.”

If the flame goes out again, this usually points to a thermocouple issue, a draft, or buildup — all of which may require service.

Preventing Future Pilot Light Problems

Regular heating maintenance is the best way to avoid frequent pilot light outages. Here are a few prevention tips:

• Schedule annual furnace inspections and cleanings to keep components clear and efficient.
• Seal gaps or cracks in furnace rooms to minimize drafts.
• Keep the furnace area clean and free of dust and debris.
• Replace aging parts such as thermocouples or worn pilot assemblies before they fail.

When to Call a Professional HVAC Technician

While some pilot light issues can be safely resolved by following the steps above, certain problems should always be left to licensed professionals, including:

• Persistent yellow or irregular flames
• Repeated pilot outages after relighting
• Suspected gas leaks or strange odors
• Broken thermocouples or pilot assemblies

A qualified technician can diagnose the root cause, ensure your furnace is operating safely, and prevent future breakdowns — saving you time and stress.

Get Fast, Reliable Furnace Repair in Northern New Jersey with Mark Lindsay and Son

If your pilot light keeps going out — or your furnace isn’t working the way it should — the furnace repair team at Mark Lindsay and Son is here to help.

Serving Northern New Jersey homeowners, our certified HVAC technicians offer same-day service, expert repairs, and trusted maintenance for gas furnaces of all types.

Contact us today to schedule service and restore your home’s comfort quickly.

CALL NOW (973) 728-8900 CALL NOW (973) 728-8900

Pilot Light Frequently Asked Questions