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What Is a Furnace Pilot Light?

What Is a Furnace Pilot Light?

Definition of Furnace Pilot Light

A furnace pilot light is a small burning flame located within the combustion chamber of your furnace. Simply known as the pilot light, this device operates as an ignition source for the burner(s) of your furnace. There are also pilot lights within gas-powered water heaters and fireplaces. A furnace pilot light is a feature exclusive to a gas- or oil-burning furnace.

How A Furnace Pilot Light Works

A furnace pilot light may be constantly burning, or may only ignite when heat is called for. Some furnace pilot lights must be lit manually, such as with a match or lighter, while others are lit electronically via an igniter whenever the system calls for heat.

There are built-in safety mechanisms that shut off the gas supply should the pilot light go out. For example, the safety designs help prevent catastrophic accidents such as carbon monoxide poisoning. Depending on your system, you may have the ability to adjust the size of the pilot light flame.

The main benefit of a furnace pilot light is that it helps to ensure there is a flame source to ignite the burner(s) within the furnace. The burners are what ultimately allows for heat to be created within the furnace to be sent throughout the home.

Best Practices for Furnace Pilot Lights

Because the furnace pilot light is responsible for a large portion of the energy consumption of your furnace, it can be wise to shut it off during warmer months. This will help save fuel and reduce your monthly costs.

Over time, the tip of a furnace pilot light can become clogged with dust and debris, especially if your furnace is located in a basement or laundry room. For this reason, it is a good idea to clean it from time to time. A qualified HVAC professional can do this as part of your regular furnace maintenance, or you can do it yourself with a bit of know-how.

In order to clean a furnace pilot light yourself, you’ll need a small toothbrush or other stiff brush. Turn off the furnace before removing the tip. Soak the tip in a degreasing solution -- a kitchen cleaner works well for this purpose -- and scrub clean with the brush. Rinse and dry thoroughly before reattaching the tip and turning the furnace back on. Cleaning your furnace pilot light tip seasonally will allow the furnace to run at peak performance.

How to Relight A Furnace Pilot Light

From time to time your furnace pilot light may go out, leaving you without heat. Some things that can cause a furnace pilot light to go out include: strong drafts, an inefficiently burning flame, a malfunctioning thermocouple, or a clogged pilot light tip.

It is important to know how to relight the pilot light. If your pilot light goes out more than once in a season, you should call a professional to investigate and remedy the cause.

Pilot Light Instructions

Your furnace’s manual should have instructions on how to relight the pilot light in the event it goes out. Any moderately capable homeowner should be able to relight the pilot light themselves in just a few steps:

  • Turn off the power to the furnace before opening the door of the unit and locating the pilot valve.
  • Turn the valve to off and wait a couple of minutes.
  •  Locate the pilot assembly, which is where a silver colored line and a copper line come together.
  • Locate the reset button.
  • Turn the pilot valve to the “pilot” position (most have three positions: off, on, and pilot). Place a lit match or lighter close to the pilot assembly. Press the reset button for approximately 30 seconds.
  • Slowly release the button and check that the flame stays lit. If not, repeat the steps above. If it stays lit you can turn the valve to the “on” position and replace the furnace door.
  • Turn your furnace back on and set the thermostat to call for heat.

If the steps above do not relight your furnace pilot light, you may have a problem with another component of the furnace that requires troubleshooting and repair from a qualified HVAC professional.

Because you are dealing with both fire and combustible gas, if at any time you do not feel comfortable performing system maintenance or relighting the pilot light yourself, it is best to contact a qualified HVAC professional who can get your heat back up and running quickly and safely.