Does your furnace start its heating cycle but the burners never ignite? A failed furnace hot surface igniter (HSI) is one possible cause.

SDG Duct Cleaning provides furnace repair in Cornwall, Ontario and throughout the surrounding SDG area. We're HVAC technicians—not just duct cleaners—and diagnosing ignition problems is a common part of troubleshooting a gas furnace that won't produce heat.

The hot surface igniter has a simple but important job. When the furnace calls for heat and the required safety conditions have been proven, the control board energizes the igniter. The HSI becomes extremely hot and is then used to ignite the gas at the burners.

If the igniter fails, your furnace can go through the beginning of its startup sequence but never actually light the burners.

What Does a Furnace Hot Surface Igniter Do?

A modern gas furnace follows a sequence of operation before producing heat.

Typically, the thermostat calls for heat, the inducer motor starts, the furnace proves the required draft conditions, and then the hot surface igniter is energized.

Depending on the type of igniter, you may be able to see it begin to glow through the furnace's viewing area.

Once the igniter reaches the required temperature, the furnace control board allows the gas valve to open and the burners should ignite.

If the HSI is broken or isn't receiving the proper power, the ignition sequence may stop before the burners light.

What Are the Signs of a Bad Furnace Igniter?

Some common symptoms that may lead us to investigate the hot surface igniter include:

• Furnace won't produce heat
• Furnace starts but burners don't ignite
• Inducer motor runs but there's no ignition
• Hot surface igniter doesn't glow
• Furnace repeatedly attempts to ignite
• Furnace eventually goes into ignition lockout
• Furnace displays an ignition-related error code
• Igniter is visibly cracked or damaged
• Furnace works intermittently
• Thermostat calls for heat but the furnace never reaches the burner stage

These symptoms don't automatically mean the igniter has failed.

The furnace still needs to be diagnosed.

My Furnace Igniter Isn't Glowing — Is It Bad?

Possibly, but not necessarily.

This is an important distinction.

If an HSI isn't glowing, there are generally two questions we need to answer:

Is the furnace actually sending power to the igniter?

and

Can the igniter operate when it receives that power?

If the furnace isn't sending power to the HSI, replacing the igniter isn't going to solve the problem.

The furnace may be stopping earlier in its heating sequence because of another fault involving the pressure switch, inducer system, venting, furnace controls or another safety circuit.

If the proper voltage reaches the igniter but it fails to operate, then the HSI itself becomes a much stronger suspect.

That's why we test before replacing parts.

Can a Furnace Igniter Look Broken?

Yes.

Hot surface igniters can become very brittle after years of repeated heating and cooling.

Sometimes a failed HSI has a visible crack or break in the element. Other times the damage isn't as obvious simply by looking at it.

An igniter should also be handled carefully. The element is fragile and can be damaged if it is handled improperly.

If your furnace isn't igniting, we can test the ignition circuit rather than assuming the HSI needs replacement based solely on appearance.

Furnace Starts but the Burners Don't Light

This is one of the most common complaints associated with furnace ignition problems.

You may hear the furnace start.

The inducer motor comes on.

You wait for the burners to light.

But nothing happens.

A failed HSI is certainly one possibility, but it's not the only one.

The furnace could be stopping before the ignition stage because it hasn't satisfied another safety requirement. There could also be an electrical or control problem preventing the igniter from receiving power.

We determine where the furnace is stopping in its sequence of operation before deciding which component needs repair.

The Igniter Glows but the Furnace Still Doesn't Light

This is another important symptom.

If you can see the hot surface igniter glowing but the burners don't ignite, the HSI may actually be doing its job.

At that point, we may need to investigate other parts of the ignition system, including whether the gas valve is being energized and whether gas is reaching the burners properly.

Again, seeing an ignition problem doesn't automatically mean the igniter itself has failed.

The sequence tells us where to look next.

Why Do Furnace Hot Surface Igniters Fail?

Hot surface igniters operate under extremely high temperatures every time your furnace starts.

Over time, repeated heating and cooling can weaken the igniter until it eventually cracks or fails.

The lifespan can vary considerably depending on the furnace, igniter design, number of heating cycles and operating conditions.

It's therefore possible for the rest of the furnace to appear completely normal while a failed igniter prevents the burners from lighting.

Furnace Igniter Diagnosis in Cornwall, Ontario

You don't need to know whether your furnace hot surface igniter has failed before contacting us.

You may simply notice:

“My furnace starts but there's no heat.”

“The inducer comes on but the burners don't light.”

“The igniter isn't glowing.”

“My furnace keeps trying to light.”

“The furnace is showing an ignition error.”

That's enough information to get started.

SDG Duct Cleaning provides furnace troubleshooting and repair in Cornwall and surrounding SDG communities during our regular service hours. We'll diagnose the furnace and determine whether the problem is the hot surface igniter or another component in the heating system.

Contact SDG for Furnace Repair

If you suspect a bad furnace hot surface igniter or your furnace simply isn't lighting, contact SDG Duct Cleaning to schedule a furnace service call.

We provide furnace repair throughout Cornwall, Long Sault, Ingleside, Lancaster, Williamstown, Martintown, Apple Hill and surrounding SDG communities.

We're HVAC technicians—not just duct cleaners.