Lighting the Pilot Light Step by Step

To turn on a heater pilot light, you will locate the pilot burner inside your furnace or water heater, set the gas control valve to "Pilot," hold down the ignition button while holding a lit match or lighter to the pilot opening, and keep the button pressed for 30 to 60 seconds after the flame appears. Once the thermocouple senses heat from the pilot flame, you can release the button, turn the gas control valve to "On," and the main burner should ignite on its own or when your thermostat calls for heat.

The exact location of the pilot light varies by furnace model. On most forced-air furnaces, you will find it near the bottom of the unit, inside the combustion chamber. On water heaters, it is usually at the base, behind a small access door or panel. Check your equipment's manual or look for a diagram printed on the unit itself—most manufacturers label the pilot location clearly.

Key Takeaways

  • Set the gas control valve to "Pilot" before attempting to light, so gas flows only to the pilot burner and not the main burner.
  • Hold the ignition button down continuously for 30 to 60 seconds after the pilot flame appears, even though the flame may seem stable sooner.
  • If the pilot does not stay lit after you release the button, the thermocouple may be dirty or faulty and will need cleaning or replacement.
  • Once the pilot is lit and holding steady, turn the gas control valve to "On" or "Heat" so the main burner can ignite when needed.

Preparing the Unit and Finding the Pilot Burner

Before you attempt to light the pilot, turn off the gas supply at the main shutoff valve for at least five minutes. This clears any gas that may have accumulated in the line. Then locate the gas control valve on your unit—it is usually a knob or lever on the side or front of the furnace or water heater. Turn it to the "Off" position and wait another minute.

Next, find the pilot light opening. On a furnace, remove the access panel or cover if there is one. You should see a small brass or steel tube pointing downward into the combustion chamber. On a water heater, look for a small opening at the base, often marked with a pilot light symbol. If you cannot locate it, check the manual or look for a label on the unit itself. Do not force any panels or covers—if something does not come off easily, you may have the wrong part.

Setting the Gas Control Valve to Pilot

The gas control valve has three positions: "Off," "Pilot," and "On" (sometimes labeled "Heat" or "Auto"). Turn the knob or lever to "Pilot." This setting allows gas to flow only to the pilot burner, not to the main burner. If you skip this step and the valve is set to "On," the main burner may ignite unexpectedly when you light the pilot, which is a safety hazard.

Some newer units have an electronic ignition button instead of a manual knob. If your unit has a button, look for a small dial or switch nearby labeled "Pilot" or "Ignition." Set it to the pilot position before proceeding. If you are unsure which position is correct, the manual will show you clearly.

Lighting the Pilot Flame

Hold down the ignition button (or the reset button, depending on your model) with one hand. With your other hand, hold a lit match, lighter, or long-reach lighter near the pilot opening. You should see a small blue flame ignite within a few seconds. Keep the ignition button pressed down for at least 30 seconds after the flame appears, even if it seems to be burning steadily. This allows the thermocouple—a heat-sensing device—to warm up enough to signal the gas valve to stay open.

If the pilot does not light after 30 seconds of holding the button, release it, wait five minutes for any gas to clear, and try again. Do not hold the button for more than 60 seconds continuously, as this can flood the combustion chamber with gas. If the pilot still will not light after two or three attempts, stop and check for a clogged pilot opening or a faulty igniter.

Releasing the Button and Switching to On

Once the pilot flame is burning steadily and you have held the button for 30 to 60 seconds, slowly release the button. Watch the pilot flame for the next 10 to 15 seconds. If it stays lit, the thermocouple is working correctly. If the flame goes out when ready after you release the button, the thermocouple is not sensing heat properly and may need cleaning or replacement.

If the pilot stays lit, turn the gas control valve from "Pilot" to "On" or "Heat." On a furnace, the main burner should ignite within a few seconds, or it will wait until your thermostat calls for heat. On a water heater, the main burner will ignite when the water temperature drops below the set point. Listen for a whoosh sound and look for a larger flame in the combustion chamber—this confirms the main burner is working.

Troubleshooting a Pilot That Won't Stay Lit

If the pilot light goes out as soon as you release the ignition button, the thermocouple is likely the problem. The thermocouple is a thin metal rod that sits in the pilot flame and generates a small electrical signal when heated. If it is dirty, bent, or faulty, it cannot signal the gas valve to stay open. Turn the gas control valve back to "Off," wait five minutes, and try again. If the same thing happens, the thermocouple needs attention.

A dirty thermocouple can sometimes be cleaned. Turn off the gas, locate the thermocouple (a thin rod near the pilot opening), and gently rub it with fine steel wool or a soft cloth to remove any soot or buildup. Wipe away any debris and try lighting the pilot again. If cleaning does not work, or if the thermocouple is bent or visibly damaged, it will need to be replaced—this is a job best left to a professional technician, as it involves handling gas lines.

When to Call a Professional

If you have followed these steps and the pilot light will not stay lit after two or three attempts, or if the main burner does not ignite after you turn the valve to "On," stop and contact a licensed HVAC technician or plumber. Do not attempt to force the system to work, as this can create a safety hazard. A professional can diagnose whether the problem is a faulty thermocouple, a clogged pilot opening, a broken igniter, or a gas valve that needs replacement.

Also call a professional if you smell gas during or after the lighting process, if you hear a loud pop or bang when the main burner ignites, or if the flame is yellow or orange instead of blue. These are signs of a problem that requires informed attention. In the meantime, turn off the gas at the main shutoff valve and open windows to ventilate the area.

Frequently Asked Questions

How long should I hold the ignition button down?

Hold it for 30 to 60 seconds after the pilot flame appears. This gives the thermocouple time to heat up and signal the gas valve to stay open. Holding it longer than 60 seconds is unnecessary and can flood the chamber with gas.

What if I don't have a lighter or match?

A long-reach lighter or a long fireplace match works best because it keeps your hand away from the pilot opening. If you have neither, a regular match held with tweezers or pliers can work, though it is less safe. Do not try to light the pilot without a flame source—the ignition button alone does not create a spark on most units.

Why does the pilot light keep going out?

The most common cause is a dirty or faulty thermocouple. Try cleaning it gently with steel wool, but if it goes out again, the thermocouple likely needs replacement. A clogged pilot opening, a bent thermocouple, or a failing gas valve can also cause this problem.

Should the pilot flame be blue or yellow?

The pilot flame should be blue with a small yellow tip at the very top. A flame that is mostly yellow or orange means the pilot opening is clogged with dust or debris. Turn off the gas and clean the opening with a thin needle or compressed air before trying again.

Do I need to relight the pilot every time the furnace shuts off?

No. Once the pilot is lit and the thermocouple is working, the pilot flame should stay on continuously. The main burner will turn on and off as your thermostat calls for heat, but the pilot should never go out on its own. If it does, there is a problem with the thermocouple or gas valve.