Why Your Heater’s Pilot Light Keeps Going Out – and How to Fix It

Few things are more frustrating than a heater that refuses to stay lit, especially when you need it most. If your pilot light keeps extinguishing, it’s not just an inconvenience — it often signals an underlying problem that affects heating efficiency, safety, and energy bills. Newton Heating and Plumbing has decades of experience diagnosing and repairing heating systems across the region. In this comprehensive guide, we explain the most common reasons why pilot lights fail, walk you through safe troubleshooting steps, and tell you exactly when it’s time to call a licensed professional.

Before attempting any repairs, remember that gas appliances can be dangerous. If you smell gas at any time, leave the building immediately and call your gas company or 911 from a safe location. The tips below are intended for homeowners with basic DIY skills; always consult a qualified technician if you are unsure.

How a Pilot Light Works

In older heating systems, a standing pilot light burns continuously to ignite the main burner when the thermostat calls for heat. The pilot flame heats a small sensor called a thermocouple (or thermopile in some models). The thermocouple generates a small electrical voltage that keeps the main gas valve open. If the pilot flame goes out, the thermocouple cools down, the voltage drops, and the safety valve closes automatically to prevent unburned gas from escaping. That’s a critical safety feature — but when the pilot repeatedly goes out, something is disrupting the flame or the sensor.

Common Causes of a Pilot Light That Keeps Going Out

Understanding why your pilot light fails is the first step toward a lasting fix. Below are the most frequent culprits, from simple maintenance issues to component failures.

1. Gas Supply Problems

Insufficient gas flow can cause the pilot flame to be weak, yellow, or intermittent. The gas valve may be partially closed, or there could be a disruption in the supply line. In some cases, low gas pressure from the utility company is the root cause. Check if other gas appliances in your home are also experiencing issues — if multiple units are affected, the problem may lie with your gas supplier rather than your heater.

2. Thermocouple or Thermopile Failure

The thermocouple is a small copper rod positioned directly in the pilot flame. Over time, it can become coated with carbon deposits, corroded, or simply worn out. When that happens, it no longer generates enough voltage to keep the gas valve open. Similarly, a thermopile (a device that produces more voltage for electronic ignition) can fail after years of thermal cycling. A faulty thermocouple is one of the most common reasons standing pilot lights go out.

3. Dirty or Clogged Pilot Orifice and Tube

The pilot tube delivers a small stream of gas to the burner. Over months and years, dust, lint, spider webs, and other debris can partially block the orifice. This restriction produces a weak, fluttering flame that is easily extinguished. In some cases, the flame may also lift away from the thermocouple due to insufficient gas flow.

4. Drafts and Airflow Disruptions

A steady, strong pilot flame needs still air. Drafts from open doors, windows, ceiling fans, or forced‑air vents can blow the flame away from the thermocouple or even snuff it out. This is especially common in basements, attics, or utility closets where the heater is exposed to outdoor air infiltration. Even a slight gust can cause the safety circuit to shut off the gas.

5. Faulty Pilot Light Assembly

Physical damage to the pilot assembly — cracks, misalignment, or corrosion — can prevent the flame from properly contacting the thermocouple. The assembly may also corrode or develop leaks over time. If the flame appears erratic, lifts off the burner, or produces soot, the entire assembly may need replacement.

6. Gas Valve Defects

In rare cases, the main gas valve itself is the culprit. Internal mechanical failures, solenoid coil issues, or electronic control board problems can cause the valve to close intermittently. This type of issue usually requires professional diagnosis with specialized tools.

Troubleshooting Tips: Step-by-Step Guide

If your pilot light keeps going out but you feel comfortable performing basic maintenance, follow these steps. Always turn the thermostat to “off” and set the heater’s gas valve to “pilot off” or “off” before touching any components. Wait several minutes for any lingering gas to dissipate.

Step 1: Verify the Gas Supply

Locate the gas shut‑off valve near your heater. It should be fully open — the handle should be parallel to the pipe (not perpendicular). If it’s partially closed, turn it fully open. Also check your gas bill or contact your utility to confirm there are no service interruptions or low‑pressure issues in your area. If you suspect a leak (rotten‑egg smell, hissing sound), do not proceed — leave your home and call for help.

External resource: Energy.gov – Furnace Maintenance Basics

Step 2: Inspect and Clean the Thermocouple

After turning off the gas and letting the heater cool, locate the thermocouple. It is usually a thin copper tube that runs from the gas valve to a point near the pilot flame. Examine it for obvious damage, bends, or heavy soot. Use a soft cloth or fine emery cloth to gently polish the tip of the thermocouple where the flame contacts it. This can remove carbon buildup that insulates the sensor. If the thermocouple is bent, carefully straighten it so the tip sits directly in the pilot flame (approximately 1/4 to 1/2 inch above the burner). If cleaning doesn’t solve the problem, replacement is often the next step.

External resource: The Family Handyman – How to Clean a Thermocouple

Step 3: Clear the Pilot Tube and Orifice

With the gas off, use a small wire brush or a can of compressed air to blow out any debris from the pilot tube opening. A thin needle or wire — specifically designed for pilot cleaning — can gently dislodge stubborn blockages. Be extremely careful not to enlarge the orifice or damage the tube. After cleaning, re‑light the pilot and observe the flame: it should be a steady blue cone, not yellow or orange, and it should fully envelop the tip of the thermocouple.

External resource: This Old House – Pilot Light Won’t Stay Lit? Fix It Yourself

Step 4: Eliminate Drafts and Airflow Issues

Check the area around your heater for any obvious sources of moving air. Close doors and windows in the room. If the heater is in a utility closet, ensure the louvered door isn’t creating a cross‑draft. Use a smoke pencil or a piece of tissue to detect drafts. Seal gaps around pipes, ducts, and foundation walls with caulk or expanding foam. For persistent drafts, a simple cardboard or metal shield can be placed temporarily to block the airflow — but make sure it does not obstruct combustion air supply for the burner.

Step 5: Relight the Pilot Correctly

After cleaning and adjustments, relight the pilot according to the manufacturer’s instructions. Most units require you to hold down the reset button on the gas valve for 30–60 seconds after lighting the pilot. This allows the thermocouple to heat up and generate enough voltage to keep the gas valve open. If the pilot goes out as soon as you release the button, the thermocouple is likely defective and needs replacement.

Preventive Maintenance to Keep Your Pilot Light Burning

Once you’ve solved the immediate problem, take these steps to reduce the likelihood of future pilot outages:

  • Schedule annual professional inspections. A licensed technician from Newton Heating and Plumbing can clean burners, test safety controls, and adjust gas pressure for optimal performance.
  • Keep the area around your heater clean. Vacuum dust and debris from around the pilot assembly and burner compartment. Avoid storing boxes or combustible materials near the appliance.
  • Install a carbon monoxide detector. Any gas appliance carries a risk of carbon monoxide (CO) accumulation. Alarms provide early warning, especially if the pilot light goes out and gas continues to leak (though safety valves usually prevent this).
  • Upgrade to an electronic ignition system. If your heater is more than 20 years old, consider replacing it with a modern system that uses intermittent pilot or hot surface ignition. These models eliminate standing pilot issues and improve efficiency by 10–20%.

When to Call a Professional

While basic troubleshooting can resolve many pilot light issues, some situations require expert intervention. Contact Newton Heating and Plumbing immediately if:

  • You smell gas, hear a hissing sound, or suspect a leak.
  • The pilot flame is yellow, orange, or unsteady after cleaning — this may indicate a gas pressure or air mixture problem.
  • The thermocouple or pilot assembly is visibly damaged, cracked, or corroded.
  • You have tried all the steps above and the pilot still goes out after a short time.
  • The heater cycles on and off repeatedly (short cycling) or fails to ignite at all.
  • You are not comfortable working with gas appliances — safety always comes first.

Our technicians are trained to diagnose and repair all makes and models, from gas furnaces and boilers to water heaters and pool heaters. We arrive with specialized tools, replacement parts, and the knowledge to get your system running safely and efficiently.

External resource: National Fire Protection Association – Heating Safety

Final Thoughts from Newton Heating and Plumbing

A pilot light that keeps going out is more than an inconvenience — it’s a signal that your heating system needs attention. By following the troubleshooting steps in this guide, you can often identify and correct simple problems like a dirty thermocouple or a drafty location. However, if the issue persists or you have any doubts about gas safety, don’t hesitate to call a professional. Newton Heating and Plumbing is committed to helping you stay warm and safe all winter long. Contact us today for a service appointment or if you need emergency repairs — we’re here to help.