How to Spot a Faulty Furnace Ignitor

Though furnaces vary plenty from model to model, type to type, they all have oneTechnician Repairing Furnace component in common, an Ignitor. Of course, the form of this component itself does vary. Gone are the days where the word “furnace” referred specifically and only to a system in which a small, always burning pilot light would burn away and light the fuel that warmed the home. Nowadays your furnace could run on anything from electricity, to gas, to oil.

But, regardless, if you’ve got a furnace, you’ve got a furnace ignitor. And like all complicated machinery, this Ignitor can sometimes develop problems. Even if you know absolutely nothing about how your furnace works and what the various components hidden away in its insides do, with some simple troubleshooting, you can determine whether your furnace ignitor is giving you problems and what the likely culprit is. And that’s what this tip of the day will aim to do, arm with all the knowledge you might need to spot a faulty furnace ignitor and get your heating back up to full working order.

Defining the Ignitor’s Role

Before we illuminate a full picture of the problems that can develop in furnace ignitors and how to troubleshoot them, one first has to understand what exactly the ignitor does, a little about how it does it, and how it fits into the grand scheme of a heating system.

What Is a Furnace Ignitor?

The furnace ignitor is a core component of the heating system. In fact, you might say it’s THE key component. It sets off the whole process of fuel burning, air warming, and warmth spreading. In the simplest sense, a furnace ignitor is the part of your heater that turns fuel into heat. Your ignitor lights the burner, sparking the combustion process. That’s the simple way to describe it. But, as you might expect, there’s a lot more to it than that.

What Is a Pilot Light?

In the past, furnaces used pilot lights that provided a flame that ignited the gas released by burners, starting the heating process.  A pilot light is a standing flame that’s always burning because it maintains a constant link to a small flow of gas. And, to be sure, your furnace might still use this system, especially if it hasn’t been replaced in the last 10 to 15 years (which by the way, it’s probably time for you to consider a replacement).

This old furnace ignition type hasn’t been phased out completely and still gets the job done to be sure. But as you might imagine, there are certain inefficiencies and risks involved in keeping an open flame burning constantly in the home via a constant stream of gas fuel. Thus, comes the electric ignitor.

Benefits of Choosing an Electric Ignitor

Newer furnaces typically use electric hot surface ignitors because this system is more dependable. It also saves you money on your utility bill since it doesn’t require a steady stream of fuel to keep it burning the way a pilot light does.

How Does an Electric Furnace Work?

Electric furnaces will have a thin wire that, once it receives an electric signal, will glow red hot and create a spark that sets off the heating process. These components are generally made of high heat resistant materials like silicon carbide or silicon nitride, both of which are able to create and withstand sparks hot enough to create a combustion reaction.

Electric Furnaces & Electric Ignitors

If you have an electric furnace in your home, though, you might have a different kind of electric ignitor. It works more like a traditional ignitor in that there’s a pilot light involved. Except, instead of being a small flame, it consists of a component that produces a small spark. It’s called an intermittent pilot because it only sparks when needed, hence the term “intermittent”.

How Does an Intermittent Pilot Work?
  • Intermittent designs use a small spark to ignite the pilot and burner.
  • When an electric signal is sent to the burner, a solenoid releases gas into the pilot and warms a heating element or emits a spark to ignite the gas.
  • The burner is then activated and warms the home.
  • The burner and pilot shut off when the correct temperature is reached.

Intermittent designs boost the efficiency of your home and present less danger in the case of a malfunction.

Signs of a Bad Furnace Ignitor 

There are a couple of tell-tale signs that there’s something up with your furnace ignitor and knowing what they are is important because a faulty ignitor is not a problem you want to ignore.

How to Tell If Your Furnace Ignitor Is Bad

  • The most obvious sign that your furnace ignitor is bad is that it won’t ignite, and this generally manifests itself in your furnace failing to run when you activate it. One word of caution though: this can also be caused by other issues, some of which are electrical. You should do simple things like checking to see if the circuit breaker for your furnace has been switched before calling an expert to check on your bad ignitor.
  • If you have an electric furnace with a hot surface ignitor, simply watch the furnace the next time it tries to start up. There is a chance that if your furnace was trying to start and didn't, it may be in a lockout phase. This is a safety default of your furnace and can be over-ridden by shutting off the main power to the unit, waiting approximately 60 seconds, and then turning it back on again. Now your furnace should try to restart so watch and listen. You should see your hot surface ignitor begin to glow followed by a "tick" sound. This "tick" is the gas valve opening. Finally, you should see the flames ignite. No glowing? Your hot surface ignitor is bad. At least that will be the case most often.
  • If you end up evaluating your circuit breaker multiple times and find that the switch for your furnace has been flipped, you could have a voltage issue related to your ignitor. This bad ignitor issue can be dangerous because you’re dealing with lots of electricity. The best course of action in this situation is to call a heating professional.

Relighting a Pilot Light

If your furnace has a pilot light, whether it be electric or gas, it might be that the light has simply gone out. It shouldn’t happen often, and it’s definitely a sign of a deeper issue if it does, but you could try relighting the pilot light.

It might be helpful to first check your furnace’s instructions. Every furnace should have a label on it that tells you how to light a furnace. Sometimes, however, the printing may be small or the furnace area may be dark. In these cases, the label may be difficult to read. Keeping the following instructions near your furnace or in another safe spot where they can be located easily will make the task much easier. Generally, though, the process will go as follows.

How to Relight a Pilot Light on a Furnace

  • First, check the power. The power switch to your furnace should look like a light switch. Make sure it’s in the on position.
  • Then, for safety’s sake, turn off the furnace itself before proceeding. Turn off your furnace’s power and gas supplies and wait several minutes for the gas to clear.
  • Most electric furnaces have an ignition button with a smaller red button next to it. Press the two buttons simultaneously. If your pilot lights, release the ignition button and hold the smaller, red button for one minute.

Other Solutions to Try If You're Still Dealing with a Faulty Ignitor

Sometimes simply resetting the pilot light won’t solve the issue. If your furnace ignitor is acting up, try some of these other troubleshooting actions.

Furnace Ignitor Troubleshooting

  • Make sure your furnace air filters are clean and regularly replaced. Dirty filters restrict airflow and affect the overall performance of your furnace. Swap out your older or clogged filters once every few months, or however often they get dirty or check the manufacturer’s instructions for a more exact timeline.
  • The gas line itself may be to blame. Your furnace’s gas line has an on-off valve. Be sure the valve isn’t off or partially closed.

If none of these troubleshooting measures solve your ignition problems, it’s time to call in a heating repair professional.

The Importance of Hiring a Professional to Repair Your Furnace Ignitor 

Fixing most furnace-related problems requires expert knowledge of gas and electrical systems. A mistake during a DIY repair can lead to gas leaks, carbon monoxide leaks, and other hazards. Tackling furnace repairs yourself can also result in expensive mistakes and recurring malfunctions. An HVAC professional will identify your problem and provide an appropriate solution.

Call AC Express at (512) 866-5520 today for more information and to get professional heating services you can depend on!

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