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The Warning Signs of a Faulty Furnace Ignitor

The Warning Signs of a Faulty Furnace Ignitor

The Warning Signs of a Faulty Furnace Ignitor

When winter temperatures are here, you don't want to deal with issues heating your home. Waking up to a cold house or spending the day in a frigid office with a broken furnace can ruin your day.

It can seem like your Furnace goes out when you need it most. Even with preventive maintenance, your Furnace can misbehave on the coldest days of the year. Sometimes it's a quick fix. In other cases, you could have a faulty furnace ignitor.

What is the furnace ignitor? How do you know if it's a problem? Keep reading everything you need to know about your furnace ignitor and what to do if the warning signs point to a problem.

Table of Contents

How Does a Furnace Ignitor Work?

Older furnaces used a pilot light to heat the air blowing into your home. Every year before the temperatures dropped, you probably noticed your parents bravely light the pilot light in the Furnace.

Today, the furnace igniter replaces the open flame of the pilot light in most furnaces. Without the ignitor, your heater won't blow hot air. It's a critical part of your furnace system and one of the most common reasons your Furnace doesn't work correctly.

You've probably heard the "click" from your Furnace before the air starts blowing. When the thermostat kicks on to start the Furnace, the ignitor creates a spark that "ignites" the gas connected to your heater. Other types of igniters heat without a spark. Instead, these ignitors heat up and touch the surface of the gas to heat the air blowing from the Furnace.

No matter which type of ignitor is in your Furnace, this chain of events lights your heater so that it blows hot air.

Don't worry—an ignitor that goes bad is common for most furnaces. Fortunately, you can replace the ignitor without replacing the whole Furnace. Most ignitors last about seven years. Keep reading to learn how to tell if your furnace problem is a faulty ignitor.

How Do I Know If There's a Problem?


A furnace that doesn't work could have a variety of issues. Some of the most common symptoms could cause several different problems. Here are a few indications that you have a faulty ignitor.

No Cold Air

If you have a faulty furnace ignitor, it won't produce that tiny spark to heat the air coming from your Furnace. Your heater blows air at the same temperature as the cold outside air without it.

Cold air blowing through your vents is a good sign that you have a heating problem within the Furnace. However, there could be a more straightforward fix.

  • Check the thermostat to ensure the setting is "heat" instead of "cool."
  • Ensure the temperature is set high enough to tell the Furnace to blow hot air.

If the thermostat's setting is okay, the next simplest solution could be a problem with the ignitor.

The Furnace Won't Come On.

If you notice your home getting colder and colder, yet the Furnace never comes on, no matter how high you set the temperature, this could indicate a problem with the ignitor.

Perform the thermostat checks mentioned above. Next, check your breaker box and make sure the switch connected to your Furnace hasn't tripped to "off." Here's how to find it if you've never needed to locate your breaker box.

Take a look at the switch that controls the power to your Furnace. If the furnace breaker is "on," there could be an issue with the ignitor, or you could have a more significant electrical problem.

The Furnace Suddenly Stops Blowing

Your Furnace has built-in fail-safes to keep you and your house safe when there is a problem with the system. If you enjoy the warm air from your Furnace, but it suddenly stops blowing, that could indicate a sudden problem with the ignitor.

  • Check the air filter. If it's dirty, air can't flow properly through the Furnace. This could cause your Furnace to stop blowing.
  • Check for debris where the air filter sits inside the Furnace and in your air ducts. Anything blocking airflow through the filter or your vents can cause the Furnace to shut off.

If the air passageways seem free and clear and you have a clean air filter, your next best option is to check the ignitor for a problem.

Starts, Then Stops, Then Starts Again

If your furnace goes on and off frequently, the ignitor could be the culprit. An ignitor on its way out can't hold a charge long enough to heat the furnace air. Plus, your Furnace probably has a safety feature that forces your system to wait at least 60 seconds before it starts again.

Repeatedly going on and off is bad for your Furnace. To save yourself from a more significant furnace issue, look for the problem as soon as you notice it cycling on and off a few times.

Tripping the Breaker More Than Once

Furnace Breaker Switch

We mentioned checking the furnace breaker to make sure it's on. However, if your Furnace keeps tripping the breaker soon after it starts blowing air, the culprit could be a faulty ignitor.

Repeatedly tripping the breaker is terrible for your Furnace and your home's electrical system. While a faulty furnace ignitor can be a simple fix, don't let the Furnace continue to trip the breaker more than twice. Leave the breaker set to "off" while repairing the furnace problem.

I Hear the Click, But Nothing Happens

That "click" we mentioned earlier is the sound of your ignitor trying to warm the fuel in your Furnace. However, if you hear the click but the air doesn't blow soon, you could have a dangerous ignitor problem.

Before you get further inside your furnace system to check the condition of the ignitor, be sure you know what to look for and how to get to it!

What Causes a Furnace Ignitor to Fail?

There are a variety of reasons why your furnace ignitor may fail.

On the one hand, it may simply be that the ignitor is too old. Again, most ignitors last around seven years. So if yours is about that old, you may need a new ignitor.

But there are other potential reasons too.

Flame Sensor Problems

Regardless of your furnace model, it comes integrated with an ignition sensor to prevent dangerous explosions. The Furnace only ignites when a flame sensor confirms a pilot flame and sends voltage to the gas valve.

The process ensures that the system does not turn on without fire and prevents gas buildup. In older furnace models, the thermocouple was responsible for this task.

When the Furnace lacks cleanliness, these sensor devices tend to malfunction. A burner caked in debris obstructs the gas supply and sends a false alarm to the sensor. The sensor, therefore, shuts the flame off.

Simple cleaning will help you get rid of the soot-covered rods. If the damage is too extensive, you might have to look into a complete replacement. Consult the user manual or the model number to buy a suitable replacement sensor. You can access the senor through the access panel.

However, don't try the replacement at home unless you have a knack for mechanics. An incorrectly installed sensor could worsen the situation. Hire an HVAC technician to do it correctly.

Short Circuit

You can expect gas furnace ignitors to handle a 120 volt electric supply from the household circuit. This electricity allows the ignitor to create a spark or heat the silicon to generate a flame. Fluctuations in this optimum range can be dangerous and cause the ignitor to short circuit.

For instance, a surge in the supply would lead the circuit breaker to overload and trip. This would obstruct the electric connection and produce no ignition. You can risk flipping back the breaker switch once to test the situation. However, if it continues to switch, a professional must examine your home's electric current and wiring system.

How Do I Check the Ignitor?

Furnace Repair Tools

If you're comfortable getting up close and personal with your Furnace, the ignitor can be easy to find and repair.

Before opening any panels on your Furnace:

  • Make sure to unplug the Furnace from the wall. You don't want any power to the Furnace while attempting to find the ignitor and replace it.
  • Turn off the gas valve. Please make sure no gas flows into the Furnace while you work on it.
  • Make sure the Furnace is at room temperature before opening any panels. A hot furnace can burn you if you touch it.

Getting to the working components of your Furnace can be dangerous! Make sure it's safe before going further.

You need to gain access to the ignitor. Remove the service panel located at the side of the Furnace. If the panel has screws or knobs, use a small nut driver to unscrew it.

Now, you can see the various components and connections of the system in front of you. Locate the ignitor among them.

What Does a Gas Furnace Ignitor Look Like?

You'll need to know what the ignitor looks like to make sure you don't mess with the wrong parts inside your Furnace. After removing the burner panel door from the Furnace, look for a small device connected between the electrical wires and the Furnace near the gas input.

  • A typical surface ignitor has a white ceramic base with a flat metal surface coming from it.
  • Spark ignitors often have two metal prongs that generate the spark.

After you've located the ignitor, see if you can identify a problem with it.

What Are Possible Ignitor Problems?

A faulty ignitor can be caused by any one of several problems:

  • Old and worn out. If the ignitor is old, it might be at the end of its life. It's time to replace it.
  • The wrong one. Your Furnace needs the right kind of ignitor to work. Even if it worked, if it was the wrong ignitor, you should replace it.
  • Bad limiter switch. If it's faulty the switch shuts off your Furnace if the temperature gets too hot.
  • Overpowered. If the breaker box blows when the Furnace comes on, your ignitor can't handle a power surge.

Without the tools and knowledge to test your ignitor, it can be challenging to identify the problem. In any case, visible damage indicates a faulty igniter.

Consult your Furnace's manual. If you need to replace the ignitor, buy the right one.
If you can't see any damage, there may be a mechanical problem. Turn your power supply back on and observe.
  • The inducer motor should kickstart working. If the thermostat is heating, energy will flow through the wires, making the inducer motor work. It fails to start if the voltage is insufficient.
  • The pressure switch should allow ignition. About 10-30 seconds after the inducer motor starts, you should hear a 'click' sound. This will indicate the pressure switch opened the gas valve.
  • The ignitor should activate and heat up. An ignition spark is created as the ignitor energizes the gas valve. The ignitor should glow orange/yellow.

You should be able to observe these activities in the system. In case any of them fails to occur, move to the next stage of this diagnosis.

Call a professional! Your safety and your Furnace are at risk when you attempt a repair yourself. Only proceed if you are confident about your mechanical abilities.

Frequently Asked Questions

Below are a few of the most frequently asked questions about furnace ignitors.

How Long Do Furnace Ignitors Last?

Most furnace ignitors last about seven years. The lifespan of your furnace ignitor will depend partly on how well maintained your system is. Regularly changing furnace filters and scheduling yearly technician maintenance is key to getting the most out of your ignitor.

What Happens When the Ignitor Goes Bad on a Furnace?

The furnace ignitor is what creates the small spark needed to heat the air coming from the Furnace. Without that spark, the Furnace can only circulate air that's being brought in from outside, whatever temperature that may be.

As a result, if you notice your ignitor's gone out, be sure to take the steps needed to replace or repair that ignitor, whether that's doing it yourself or calling a professional.

How Do You Know If Your Furnace Ignitor Is Bad?

Turn off the power and let the Furnace cool down. You can perform a multimeter test to find out exactly whether the ignitor is at fault. Here's how to do it:

  • Disconnect the wiring that connects the ignitor to the surface.
  • Turn the power back on and wait till the inducer motor starts working.
  • Grab a multimeter to check the voltage going to the ignitor connection.
  • Gently put the probes of the meter inside the plug. Make sure you only touch the tips of the plug and not damage it by pushing the probes through.
  • If the value on the meter reads anything above or below 120 volts, the ignitor is bad.

Based on the tests, do not delay consulting a heating and cooling company to replace the ignitor.

What if the ignitor is not at fault? In that case, find out the common problems associated with furnaces and try locating the issue. The best way would be to get a professional furnace repair done.

How Do You Diagnose a Bad Ignitor?

Furnace Repair Man It is also possible that the ignitor may not be the real culprit.

To truly diagnose the problem, you will have to check up on some other components. This small troubleshooting process includes canceling out potential problems in the surrounding parts one by one.

  • Thermostat. The Furnace will only ignite if the thermostat is functional. Double-check that the temperature is set higher than the temperature of the surroundings. If you have a programmable device, check for an error code. Once you've inquired about all these matters, restart your thermostat.
  • Gas Valve. The handle to the valve must rest parallel to the gas pipe when the connection is secured. Once you have confirmed that the valve is working, turn on any gas appliance in the house. If there is no gas pressure, the fault lies in the stability of your connection, not the Furnace.
  • Air Filter. If your furnace filter is dirty, it will block the airflow from reaching the heat exchanger. This will overheat your system, causing the ignitor to shut off. You will find the filter inside the blower compartment. Inspect the extent of damage and accordingly either clean it or go for a replacement.
  • Burner. Apart from an unstable connection to the gas supply, dirt and debris can also damage the burners. They will fail to provide sufficient natural gas for heating. Although the ignitor will activate, it will shut down when the temperature is not hot enough. Attempting to clean a gas-powered burner can be dangerous without professional help.

How Often Should a Furnace Ignitor Be Replaced?

On average, furnace ignitors will last about four to seven years. This depends upon how well maintained the system is. After the seven-year mark, you should replace it. The Furnace itself can easily last you for 20 years or more with proper maintenance.

Don't Ignore the Warning Signs of a Faulty Furnace Ignitor

At the first signs of a faulty furnace ignitor, take action. Investigate the symptoms on your own, then call a professional to handle a repair. An ignitor repair or replacement is often an inexpensive fix that can save you from more significant (and expensive) furnace repairs. A professional repair can also protect you from injury or accident.

Allow St. Louis' Finest Technicians to Save the Day

Don't suffer without furnace heat! Let Crystal Heating and Cooling take over the job for you. Once you've discovered a problem with your furnace ignitor, contact us to schedule a furnace repair or maintenance. Our technicians are standing by to help you get your Furnace back in peak working condition.

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