How To Tell If A Furnace Igniter Is Bad (Here Are Some Telltale Signs)

Ryan Womeldorf
by Ryan Womeldorf

Of all the components within your furnace, there are a couple that are vastly more important than the others. When one of those components gets worn down or stops working, it can mean the difference between a comfortable home and having to be huddled up in blankets in your own home.

One of those components is the furnace ignitor. The ignitor plays an integral role in providing warm air to your home. When it stops running, there are a few signs to look for. Your furnace might blow cold air, have shorter than normal cycles, won’t have a glow, or your furnace won’t start at all.

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What Does the Igniter Do?

If it sounds self-explanatory that’s because it kind of is. The igniter does just that. It lights the burner, sparking the entire combustion process. This is how the air gets warmed before being distributed through the vents and into your home.

If the igniter doesn’t do its job, the combustion process never begins. And when it never begins, your home doesn’t warm up as it should. So, to say that the igniter plays an integral role would be putting it lightly.

No Glow Igniter

Depending on the age of your furnace, you may have what is known as a no glow ignitor. The newer furnaces use an electronic ignition as opposed to the traditional pilot light. The ignitor has replaced the old pilot lights because of safety issues with the pilot.

When looking for the ignitor, you would look in the same place that you would traditionally do so when looking for the pilot light. When your first starts, the ignitor should have a glow. It has to get super-hot in order to ignite the air and gas mixture required for proper combustion. If you don’t see a glow, it means the ignitor has gone bad.

Blowing Cold Air

Another sure sign that your furnace’s ignitor is bad is that you are getting cold air instead of warm. Unless you have set the thermostat to the COOL setting, the furnace should be pumping out warm air. Thankfully, there’s a faster solution to try.

Check the thermostat. More often than not, this is the case of the thermostat being set improperly. Make sure that it is set for HEAT and AUTO before checking anything else. It is the easiest, quickest fix in most cases.

If the thermostat is correct and you’re still getting cold air, the ignitor could be the main culprit. This is a clear sign that the burner isn’t being lit and that there is no combustion being created. Without that combustion, you don’t get heat. It’s as simple as that.

Short Cycles

This one can be a bit tricky to diagnose. Your furnace may start cycling. This may be where the furnace goes on as normal but isn’t regulating temperature, instead just kind of going through the motions before clicking off again.

When the furnace turns on and off on a regular basis, this is known as short-cycling. This is a built-in safety feature that the furnace implements when it senses a problem that puts safety into question.

While it can be other issues, short-cycling can definitely be caused by a faulty ignitor. Call in an HVAC technician to troubleshoot the issue and look for potential issues. When it comes to safety, nothing should be ignored or underestimated.

The Furnace Stops Running

When the furnace won’t run at all, one of the first places to look is the ignitor. This is because the furnace will shut down completely if there is an ignition problem. Shutting down is a safety measure meant to protect you and the rest of the furnace.

If the furnace isn’t igniting or turning on at all, it could be an apparent sign that the ignitor should be replaced. Just be careful not to jump to conclusions as it isn’t a certainty that the ignitor is bad, and it could be something else entirely.

Diagnosing the Furnace Ignitor

There are thankfully a couple of steps that you can take to diagnose the ignitor. Having no heat is a clear sign but there are a couple of other things that you will want to check if the furnace is otherwise running.

  • Thermostat. As mentioned previously, it can be as simple as an improperly programmed thermostat. Make sure that the thermostat is set to HEAT and that the temperature is set above that of the current temperature in the house.
  • Inducer motor. Upon startup, you should hear a motor. This is the inducer motor. It is meant to get airflow going through the combustion chamber and out into the chimney. That action should create a vacuum that gets rid of the harmful exhaust containing carbon monoxide.
  • Nothing happens. Should those two things be fine, and nothing is happening, there are a few things to consider. The thermostat is bad, which can be replaced cheaply. The inducer motor will need to be replaced. The pressure switch, which is designed to sense that vacuum, is bad. Or the control board is bad, which can be quite expensive to replace as it is an electrical issue.

A Few Other Things to Check

When diagnosing the problem with your furnace, there are a few other things worth checking before calling for repair. These may or may not help you diagnose the problem yourself and can even, in some cases, be given a do-it-yourself fix.

  • Check the breaker. Another fairly common issue is that the circuit breaker can trip. In your control panel, it should be labeled accordingly. When it gets tripped, it will be in a middle position instead of distinctly on or off. If the furnace starts up but the breaker winds up tripping again, you have an electrical problem on your hands.
  • On/Off switch. It is entirely possible that the off switch could have been triggered, especially in the wake of changing out the filter. It isn’t necessary to turn the furnace off when changing the filter but can happen as a result.
  • Chimney vent. Finally, only do this if you can get safely to the roof. Ice, snow, and even a bird’s nest can clog up this vent. When it is blocked, there is no vacuum created. The pressure switch will notice this, and the furnace will turn off accordingly.

What is the Cost of Replacing a Furnace Ignitor?

Let’s say that you determine the furnace ignitor to be the problem. What kind of costs are you looking at to replace it? The answer to that question depends on whether or not you do the job yourself or go with a professional service.

Doing the repair on your own can cost as little as $15 but it isn’t advised that someone completely inexperienced do the job. There is plenty that can go wrong, and it is always advised. Even if you save on the repair itself, there are things that can go wrong that lead to further, more expensive repairs down the road. That can all be avoided.

Professional repair. If you do opt to go the professional route, the costs can vary. The bill for a professional repair can range from $75 all the way up to $200. The part itself is relatively cheap — $15 to $60 – and it only takes about 10 minutes to fix. But most repair companies will have a minimum service fee, generally in the $75 range.

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When Should I Replace my Furnace Ignitor?

There is a Gas Furnace Guide that dictates industry averages. According to them, ignitors tend to have an average lifespan in the four to seven-year range. So, when those seven years have passed, it’s probably a good idea to replace it even if it is working fine.

The good news is that you won’t have to replace the entirety of the furnace since the other parts can last up to 15 years. How long it works depends on the level of maintenance that you are providing. Regular maintenance can be a great way to extend the life of the components within your furnace, keeping those expensive repairs at bay.

Ryan Womeldorf
Ryan Womeldorf

Ryan Womeldorf has more than a decade of experience writing. He loves to blog about construction, plumbing, and other home topics. Ryan also loves hockey and a lifelong Buffalo sports fan.

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