What is the purpose of a pilot light?

The purpose of a pilot light is to provide a constant ignition source so the main gas burner can light quickly and safely when the appliance calls for heat.

Is a pilot light always on?

In standing-pilot systems, yes. The pilot flame is designed to stay lit so the appliance can ignite the main burner immediately.

What happens if the pilot light goes out?

If the pilot light goes out, the appliance typically shuts down. A safety device such as a thermocouple cools down and signals the gas valve to close, stopping gas flow.

Will gas leak if the pilot light is out?

Normally, no—properly working safety controls shut off gas when the pilot flame goes out. If you smell gas or the pilot repeatedly fails, stop and have it inspected.

Do all furnaces have pilot lights?

No. Many modern furnaces use electronic ignition instead of a standing pilot light.

What replaced pilot lights in modern systems?

Most newer gas appliances use electronic ignition systems that spark only when needed, eliminating a continuously burning pilot flame and improving efficiency.

What is the purpose of a pilot light?

The purpose of a pilot light is to provide a constant ignition source so gas appliances can turn on safely and immediately.

Is a pilot light always on?

Yes. In traditional standing-pilot systems, the pilot light is designed to stay on at all times so the appliance can ignite instantly.

What happens if the pilot light goes out?

If the pilot light goes out, the appliance will shut down. A safety device such as a thermocouple cools and closes the gas valve to stop gas flow.

Will gas leak if the pilot light is out?

Normally, no. Properly working safety systems automatically shut off gas when the pilot flame goes out. If you smell gas, stop and call a professional.

Is it safe to relight a pilot light yourself?

Often yes, if you follow the manufacturer’s instructions. Do not relight if you smell gas or if the pilot will not stay lit.

Do all furnaces have pilot lights?

No. Many modern furnaces use electronic ignition systems instead of a standing pilot light.

Are pilot lights outdated?

Pilot lights are not unsafe, but they are less efficient than modern electronic ignition systems used in newer appliances.

What replaced pilot lights in modern gas appliances?

Most modern gas appliances use electronic ignition systems that create a spark only when heat is needed, eliminating a constantly burning flame.

What Is a Pilot Light?

Q: What is a pilot light?

A pilot light is a small, continuously burning flame in older gas appliances that ignites the main burner when heat is needed.

Luke Barbosa
Dec 18, 2025
5 min read

Updated: Dec 29, 2025

heat and air gurus owner and operator, Luke Barbosa performs maintenance on furnace in Carrollton off of Castille Dr. This furnace today did not have a pilot light — If your furnace has a little motor like the one below my hand, you don't have a pilot light.

Last Updated: December 2025

AI Summary

A pilot light is a small, continuously burning flame found in older gas furnaces, water heaters, and fireplaces. Its job is to ignite the main burner when heat is needed. Many modern HVAC systems no longer use pilot lights and instead rely on electronic ignition for better efficiency and reliability. If a pilot light won’t stay lit, the most common causes are a failing thermocouple, airflow issues, or a dirty pilot assembly. Homeowners across DFW can contact Heat and Air Gurus for same-day diagnosis and repair.

When your furnace won’t fire up on a cold North Texas night, the issue is often simpler than you’d expect: the pilot light.

But what is a pilot light—and why does this tiny flame have so much control over your home’s comfort?

At Heat and Air Gurus, we’ve diagnosed thousands of heating problems across Carrollton, Plano, and the entire DFW metroplex. This guide breaks down everything homeowners need to know about pilot lights, how they work, when they fail, and when it’s time to call a professional.

What Is a Pilot Light?
How Pilot Lights Work
Why Pilot Lights Go Out
Safety First: When NOT to Relight
Modern Alternatives to Pilot Lights
How to Relight a Pilot Light
When to Call Heat and Air Gurus

What Is a Pilot Light?

A pilot light is a small, continuously burning flame inside gas-powered appliances such as furnaces, water heaters, and gas fireplaces. Its purpose is simple but critical: to ignite the main burner whenever heat is needed.

Think of it as a match that’s always ready. When your thermostat calls for heat, gas flows to the burner and the pilot light ignites it instantly.

Which Appliances Use Pilot Lights?

In many North Texas homes, pilot lights are commonly found in:

Gas furnaces (typically pre-1995 models)
Tank-style water heaters
Gas fireplaces
Older gas stoves and ovens

Guru Pro Tip: Most furnaces manufactured after 1995 use electronic ignition instead of a standing pilot. If you’re unsure what system you have, this image at the top explains the difference. Learn more About Furnace Sensors.

How Pilot Lights Work (Simple, Not Nerdy)

A traditional pilot system relies on three main components.

1. The Pilot Flame

A small, steady flow of gas keeps the pilot burning 24/7. A healthy pilot flame should be blue with a sharp tip, which indicates clean combustion.

2. The Thermocouple (or Flame-Proving Device)

This small copper rod sits directly in the pilot flame. When heated, it generates a tiny electrical current that keeps the gas valve open.

If the flame goes out, the thermocouple cools, the current stops, and the gas shuts off automatically. This is a critical safety feature that prevents gas leaks.

Flame Sensor vs Thermocouple (Clearing the Confusion)

Our viral video (1.5M+ views) sparked a huge debate:

Thermocouples → Used on older standing-pilot systems
Flame sensors → Used on modern electronic ignition systems

They do the same job (prove flame is present) but use different technology.

1.5M View Flame Sensor Video

3. The Main Gas Valve

When the thermostat calls for heat, the gas valve opens, fuel flows to the burner, and the pilot flame ignites it instantly.

Why Pilot Light Flame Color Matters

A pilot flame tells a story.

Blue flame → Normal, efficient combustion
Yellow or orange flame → Dirty burner or ventilation issue
Weak or flickering flame → Draft or gas pressure problem
No flame → System won’t operate

We see flame-color issues daily on service calls across DFW.

Why Pilot Lights Go Out

Here are the most common reasons we see in the field.

1. Draft or Airflow Issues

Strong airflow can blow out a pilot flame, caused by:

Open windows or doors near the furnace
Poorly sealed furnace closets
Negative air pressure in the home
Cracked heat exchangers

2. Dirty Pilot Assembly

North Texas dust builds up fast. Dirt can clog the pilot orifice, leading to weak or unstable flames.

Preventive maintenance keeps this from happening Sign up for our Prime and Wagyu Club memberships with the chat on our website OR text 469-797-1269

3. Failed Thermocouple

Symptoms include:

Pilot lights but won’t stay lit
Flame goes out when you release the button
- Guru Pro Tip: You may need to hold the button until your thumb feels like it is falling off
Repeated pilot failures

This is a common repair and requires professional replacement.

4. Gas Supply Interruptions

Gas utility work or neighborhood construction can shut off gas service, extinguishing all pilot lights in the home. Did you remember to pay the gas bill?