Furnace Pilot Light Won’t Stay Lit: Repair Solutions

You’ve relit the pilot light three times today—and it keeps going out.

You followed the instructions. You held down the button. You watched the flame catch. But five minutes later—or five hours later—it’s out again. At H&H Heating and Air Conditioning, we’ve fixed thousands of pilot light problems over the past 50 years. Sometimes it’s a quick fix. Sometimes it’s a sign of something bigger. Let us help you understand what’s going on.

How the Pilot Light Works

The pilot light is a small, continuously burning flame that ignites the main burners when your thermostat calls for heat. The key safety component is the thermocouple—a copper rod positioned directly in the pilot flame. When heated, it generates a small electrical signal that keeps the gas valve open. If the pilot goes out and the thermocouple cools, it automatically shuts off the gas supply to prevent unburned gas from building up.

Important: Standing pilot lights are found almost exclusively in older furnaces—typically 20+ years old. Newer furnaces use electronic ignition systems that are more efficient and reliable.

The Thermocouple: The Most Common Cause

If your pilot lights but goes out as soon as you release the button, the thermocouple is almost certainly the problem. This is the classic symptom.

Thermocouples fail from constant exposure to the pilot flame, soot buildup that insulates the tip, or simply getting bent out of position. The pilot flame should completely envelop the top 3/8 inch of the thermocouple tip—if it doesn’t reach properly, the thermocouple won’t generate enough voltage to keep the gas valve open.

You can visually inspect the thermocouple yourself. Look for corrosion, soot buildup, or damage to the copper rod. If it looks heavily corroded or bent, it probably needs replacement.

Think your thermocouple is the problem? It’s one of the most common fixes we do—call us for a quick diagnosis.

Dirty Pilot Orifice: Weak Flame Problems

A healthy pilot flame should be a strong, steady blue cone. If your flame is weak, flickering, yellow, or orange, the pilot orifice may be clogged with dust and carbon buildup.

A weak flame can’t heat the thermocouple properly, causing the gas valve to shut off. Yellow or orange flames also indicate incomplete combustion, which can produce carbon monoxide. If your pilot flame is anything other than strong and blue, don’t ignore it.

Cleaning a pilot orifice requires disassembling the pilot assembly—a job for a technician, not most homeowners.

Drafts and Gas Supply Issues

Drafts: Strong airflow can blow out your pilot light. If your pilot relights easily but keeps going out, check for air leaks near your furnace, ensure the access panel is secure, and inspect the flue pipe for cracks or loose connections. Downdrafts from chimneys on windy days are another common culprit.

Gas supply: Check if other gas appliances are working. If nothing gas-powered works, contact your utility company. Also verify the gas valve near your furnace is fully open (handle parallel to the pipe).

Failing gas valve: If the thermocouple has been replaced and the pilot orifice is clean but the pilot still won’t stay lit, the gas valve itself may be failing. This is a professional repair.

What You Can Safely Do Yourself

Safe DIY: Relighting the pilot per manufacturer instructions, checking the gas valve position, visually inspecting for obvious problems, gently cleaning dust from around the pilot area when cool.

Call a professional for: Thermocouple replacement, cleaning the pilot orifice, gas valve work, or anything involving gas connections.

If you smell gas: Evacuate immediately and call 911 from outside. Never ignore a gas smell.

When to Consider Replacing the Furnace

Furnaces with standing pilot lights are typically 20-30 years old. Older furnaces have AFUE ratings of 60-80%, meaning 20-40% of your fuel goes up the flue as waste. Modern furnaces achieve 90-98% efficiency—real money on your heating bills.

If pilot light problems are your only issue, thermocouple replacement is reasonable. But if you’re dealing with recurring problems or expensive repairs, consider replacement. General rule: if repairs approach 50% of a new furnace cost, replacement makes more sense.

Get Your Heat Back

A pilot light that won’t stay lit means no heat for your family. At H&H Heating and Air Conditioning, we diagnose pilot light problems quickly and give you honest options. Our technicians don’t work on commission—we have no incentive to push repairs or replacement you don’t need.

Pilot light keeps going out? Call H&H for fast, honest diagnosis.

Frequently Asked Questions