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Furnace, Boiler and Water Heater Ignitors

furnace ignitor

An ignitor, in a sense, is the catalyst that turns your furnace’s or boiler’s fuel into heat. Your ignitor lights the burner, which creates the heat within the heat exchanger. But how does the ignitor itself work?

Types of Ignitors

In the past, most furnaces and boilers used pilot lights to provide the flame that would ignite the gas released by the burners, starting the heating process. The pilot light is a standing flame that burns by maintaining a constant link to a small flow of gas. When your furnace or boiler switches on, a valve releases a larger flow of gas into the burner and that fuel is then lit by the pilot light, generating heat. To prevent safety issues in the event that your pilot light goes out, a small valve is installed that shuts off the flow of any gas when the flame dies down.

Today, you’ll find that most furnaces use electric hot surface ignitors. Experts state that this is because this system is not only more dependable, it is more inexpensive to make and use, since it doesn’t require a steady stream of fuel the way the pilot light does. The hot surface ignitor is a thin wire that, upon receiving an electrical signal, glows red hot and creates a spark that sets off the heating process. In order to create—and withstand—a hot enough spark, manufacturers often use wires made of the high-heat-resistant materials silicon carbide or silicon nitride.

Pilot Light Switch

A pilot light switch is designed to prevent premature failure of the spark igniter or glow coil in the event a lengthy gas interruption occurs while the thermostat is calling for heat. The device operates using exactly the same principle as a gas-pressure switch used in the manifold of the gas-fired furnace or boiler. The switch is installed in the pilot gas line between the pilot and its regulator. Examples of setups that include a pilot light switch include a Carrier/Bryant Glow Coil or a General Electric gas furnace with an original gas valve setup.

Types Of Pilot Light Switches

As burners have evolved, the components have evolved as well. Such is the case with pilot light switches. For an older model, an example is a Carrier 2H pilot without a glow coil and using SPDT (single pole, double throw) switch action that can be used with 11-volt glow coil systems. The main orifice is a .021, though there is a second--sized at .031 that's to be used solely as an escapement orifice. This should be used only on installations in which an escapement tube is connected between the gas valve and this orifice. A more recent model would be a thermocouple pilot light switch, such as those made by Johnson Controls. Here, a manual reset SPDT switch is used with a nominal 30 MV thermocouple. While the former looks like a large igniter or glow bar, the latter device looks like a simple, small electrical box, about 2 inches by 4 inches.

Replacing A Pilot Light Switch

As with any electrical repair, the most important step is to shut down the electricity to the furnace. The pilot light switch may be mounted by a couple of screws. Simply unscrew, then unattach the electrical wires from the metal connectors. Remove and replace with a new switch. A very simple replacement.


On occasion, your pilot light may go out as a result of drafts, requiring you to manually relight it. Dirty or broken sensors or thermocouples are other fairly common causes of an unlit pilot light.

Electric hot surface ignitors, on the other hand, have a definite shelf life. Although it may take as long as five years, your ignitor will eventually burn out. Regularly cleaning your furnace’s filters and gently cleaning around the ignitor may extend the life of this component, although you should keep in mind that handling can easily damage the fragile wire. Replacement ignitors available from wholesalers or online retailers can cost anywhere between $17 and $77, depending on the needs of your furnace or boiler. To replace the ignitor yourself, consult your furnace’s or boiler’s user’s manual, or contact your HVAC maintenance technician to do the job for you.

Question and Answer

Question: My Amana Air Command 90 furnace won't ignite.

Answer: On 2016-01-14 Gary wrote:

There are several possible reasons why your furnace won't start. It could be a problem with your ignitor, or even a problem with the thermostat. It's also very possible that there is a problem with a limit switch or with the furnace's circuit board.

Question: My furnace does not start - what's wrong?

Answer: On 2016-04-26 Gary wrote:

This can be caused by several problems, including a lack of fuel, a faulty igniter or flame sensor, or a problem with the control board. Can you see a fault code from the red light on the unit?  These codes help to diagnose a problem with the furnace.

Question: How to light the pilot light on a Carrier 58 MVP

Answer: On 2012-11-16 JB wrote:

First, according to the owner's manual you should not try to light the pilot light. In fact they say: "Never attempt to manually light the burners with a match or other source of flame."

The manual also says: "Instead of a continuously burning pilot flame which wastes valuable energy, your furnace uses an automatic, hot surface ignition system to light the burners each time the thermostat starts your furnace."

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Question: What ignitor does the Carrier 58PAV furnace use?

Answer: On 2015-02-02 Gary wrote: The Carrier 58PAV uses a hot surface ignition system. A replacement part for this model can be purchased online. The manufacturer part number of the ignitor is 332505-751.

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Question: How do you light the pilot on a Carrier Comfort 80 furnace?

Answer: On 2016-03-07 Gary wrote:

A Carrier Comfort 80 furnace does not have a pilot light. Instead, it has an igniter, which is safer. If your furnace is having trouble starting, there could be a problem with the igniter. 

Question: How to light pilot on my Carrier Performance 93?

Answer: On 2016-02-22 Eric wrote:

Here is the link to the owners manual for the Performance series. The manual covers routine maintenance and troubleshooting solutions. On page 4 it covers starting your furnace.

Question: Coleman DGAA furnace ignition fails to light.

Answer: On 2016-03-07 Gary wrote:

There could be a problem with the ignitor or the flame sensor, among other possibilities. Because of potentional shock hazards, you should have it checked out by an experienced heating contractor and not try to fix it yourself.

Question: Where is the pilot on the Frigidaire FG6RC furnace?

Answer: On 2013-02-19 JB wrote:

It doesn't have a pilot light in the traditional sense. The fuel is ignited by a hot surface ignitor, which works like a light bulb filament to ignite the fuel. It heats up without flame to a point where gas or oil can be ignited.

If your furnace is not lighting then there is a problem with it and the ignitor is either being prevented from working as a safety feature or perhaps is malfunctioning.

Question: What is igniter part number for the Goodman GMNT furnace?

Answer: On 2014-04-30 Danielle wrote: According to the repair parts catalog for Goodman 80% GMT, GDT, GMTH and 90% GMNT Gas Furnace Units ("B" and "D"Revisions Only) the igniter part number is B1401015S.

Question: How do I get the pilot to light on my GLUA90-E5A unit? It seems to have stopped working.

Answer: On 2013-02-19 JB wrote: This could be due to a range of issues, but is probably a safety feature of the furnace preventing it from lighting. If you look at your owner manual you'll probably see that there is an electronic ignition listed on the schematic of the furnace, which is how the pilot is lit. Therefore, it could be that this is malfunctioning or it could mean that there is uneven airflow through the furnace such as due to a very dirty filter or some other issue that is tripping a safety feature.

To find out more, there should be a set of lights or an LED display that you can see through a window on the furnace or by opening the front panel. If they are blinking they indicate an error code. Hopefully there is a description of the codes pasted to the furnace, which should explain how to read the codes and what they mean (I can't find a list online). You may find this in the owner manual as well.

Question: How to light the pilot for the Lennox G50UH?

Answer: On 2014-10-20 Danielle wrote: See the manual starting on page 3 on how to the light the Lennox G50UH.

Question: How much is a replacement igniter for a Lennox G60UHV furnace?

Answer: On 2016-01-26 Gary wrote:

I couldn't find a price for this particular unit, but a furnace igniter usually costs anywhere from $30-$80, and having one replaced by a professional averages $100 to $150.

Question: Where is the igniter on a Lennox furnace?

Answer: On 2016-04-26 Gary wrote:

From what I can find online it appears that the igniter is usually located inside the burner box, in front of the first burner.

Question: Where is the pilot light located on a Payne PG8JAA furnace?

Answer: On 2015-01-16 Gary wrote: The Payne PG8JAA uses a hot surface ignition, which means that it does not have a pilot light.

Question: Had a new ignitor installed last month. The furnace still does not start occasionally. If I jiggle the wires going to the ignitor I sometimes get the furnace to start. Seems like a bad connection somewhere. Any suggestions?

Answer: On 2016-03-07 Gary wrote:

You should contact the contractor who installed it because it sounds like either a problem with the wiring, the flame sensor or with the new ignitor. Because you are dealing with igniting gas, you'll definitely want to have this looked at as soon as possible.

Question: How To light the pilot on the York Diamond 80?

Answer: On 2014-06-27 Danielle wrote:

This is one of the warnings found in the manual for the York Diamond 80: "This appliance does not have a pilot. It is equipped with an ignition device which automatically lights the burners. Do not try to light the burners by hand."

Question: New Bradford White 75 gallon water heater pilot light will not ignite.

Answer: On 2016-02-19 Gary wrote:

There are a couple possible reasons why your pilot won't light. There could be a problem in the manufacturing of the thermocouple or other part of the tank. If so, it should be covered under the unit's warranty.

There may also be air in the gas line. If this is the problem, your unit won't get the gas it needs to run and you'll need to bleed the lines to get all the air out. Because gas is very combustible, it's recommended that you have a licensed heating contractor get your water heater started for the first time.

Question: My Rheem Fury water heater pilot light won't stay lit.

Answer: On 2016-04-27 Gary wrote:

There are a few possible causes for this problem, the most likely being a problem with the gas valve or thermocouple. You'll probably need to contact an HVAC professional to repair this, especially when dealing with gas.

Question: Where can I get parts for my water heater? My spark igniter is dead.

Answer: On 2016-01-14 Gary wrote:

Parts can often be purchased online through the manufacturer, although many companies will only sell to contractors. When repairing water heaters, particularly gas-fired models, it is often recommended that a professional contractor perform the work for safety reasons. 

Question: Water heater will not re-ignite after heating.

Answer: On 2016-03-15 Gary wrote:

There are several possible causes for this problem, including a faulty flame or temperature sensor, or a problem with venting or air intake.

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