Updated 04/01/24
Living in Santa Rosa, a malfunctioning furnace can be a nightmare, especially during the chilly winter months. If you notice your furnace ignitor not glowing, don’t panic. It’s a common issue that homeowners face, and it can be resolved with the right steps.
Taking care of your heating and cooling systems is crucial to avoid unpredictable problems with your furnace. As a homeowner, you understand the importance of proper maintenance to keep your furnace running smoothly. But even with diligent efforts, some issues may occur, such as a furnace glow plug that isn’t glowing. In such cases, it’s essential to identify the root cause of the problem and take the necessary steps to solve it. Don’t let a malfunctioning furnace keep you in the cold. Let our Santa Rosa experts guide you through the process of fixing your furnace ignitor.
What Role Does the Furnace Glow Plug Play in Your Heating System?
Furnace glow plugs are a common form of ignitor found in many heating systems throughout the U.S. They are responsible for making sure that your furnace can burn the fuel it uses to produce heat and warm your building. As such, this makes the furnace glow plug essential, and your furnace will not be able to run without it. If the glow plug cannot ignite the pilot, the fuel in your furnace will merely sit there unused, no matter how hard you press the buttons on your thermostat.
Reasons Your Furnace Ignitor is Not Glowing
Several things can cause a glow plug to fail, so it pays to be aware of all of them. Here are the most common causes for a furnace ignitor not glowing, along with how you can recognize each issue and what you should do to fix them if you see them occurring:
- Dirt has settled on the glow plug. Dirt on your glow plug can prevent it from successfully igniting the pilot, thus causing it to look as though it is not turning on. Dirt and dust are common culprits when it comes to failed furnace ignition because they can enter the interior of your furnace through neglected air filters and settle on all kinds of essential instruments and components. If enough dirt cakes the glow plug or pilot light, it will prevent it from being able to light the fuel in your furnace. However, you should not attempt to clean the ignitor by yourself because it is incredibly delicate and can easily be damaged by a rough touch. Instead, if you notice dirt covering your ignitor, make sure to call a professional for help. You might want to have your ducts cleaned while you’re at it since that’s probably where most of the dust is coming from. Make sure you change those filters once a month!
- The gas pressure is not high enough to supply fuel to the system. Your furnace needs at least two things to start: a functioning ignitor, and a constant stream of fuel from the gas valve that the ignitor can burn to create heat. Sometimes, the problem with a glow plug has very little to do with the plug itself at all. Instead, it may simply appear to be malfunctioning because the gas valve is unable to send enough fuel into the system and the ignitor has nothing to ignite.
- The glow plug is old and needs replacing. Despite even the most meticulous care and diligent home maintenance, nothing is made to last forever. Eventually, your glow plug may “flame out.” If this failure occurs, the only thing to do is purchase a new glow plug and replace the old one. Until you do, you will be unable to use your furnace. Fortunately, glow plugs are not expensive to purchase, with the required part typically costing under $120. Just make sure you have a licensed contractor that charges you a fair but competitive price for their labor, and you should be fine.
Dealing With a Faulty Furnace Glow Plug
As much as we appreciate having a warm house in the middle of winter, most of us have kind of a love/hate relationship with our furnaces. So far as home appliances go, furnaces can be some of the most frustrating because they require a little more maintenance than your fridge or washing machine. If you don’t stay up to date with your service appointments, you could find your furnace to be somewhat unpredictable. We recommend having every HVAC appliance in your home serviced at least once a year to make sure nothing goes wrong during peak heating and cooling seasons.
However, even if you keep up with the proper maintenance, you can still run into some problems with your furnace. One of the most frustrating ones is a faulty ignitor. This is one of the most important parts of any furnace and a malfunctioning ignitor can leave you stuck in a freezing cold house until you can get someone out to fix it. In this post, we’ll go over a few reasons why your ignitor might suddenly stop working and how you can take care of the problem and get the heat back on as soon as possible.
How a Furnace Glow Plug Works
During the winter, you might hear a clicking sound just before your furnace turns on. That’s the sound of the ignitor, a modern replacement for the pilot lights old furnaces used to have. If you grew up somewhere with cold weather, you might have memories of your parents going downstairs at the beginning of the winter to light the pilot light. Back then, igniting the pilot light was always a task that came with a little bit of apprehension. If any gas had leaked into the ignition chamber over the summer, lighting the flame on the pilot light could cause an explosion, so it felt like a bit of a risk every time.
It’s because of that risk that pilot lights were eventually phased out in favour of modern ignitors. Ignitors today are much safer since the furnace can switch them on and off automatically, saving the homeowner the trouble of lighting them every year. They also create sparks instead of using an open flame, creating a much more controlled combustion reaction in the chamber and making the furnace far less likely to blow up. In fact, today’s furnaces are filled with so many safety features that it’s almost impossible for them to suffer a catastrophic failure like that anymore.
Here’s how the ignitor works. When your thermostat detects that the temperature is getting a little too low, it sends a signal to the furnace. The ignitor switches on, creating a spark that ignites the propane or natural gas inside the furnace’s burner. As long as the gas line stays open, the burners will continue to keep an open flame, kind of like a gas stove. The heat generated by the flames is transferred up into a part called the heat exchanger, warming it up. The blower fan then switches on, blowing air across the heat exchanger. The air absorbs the heat from the exchanger before it’s blown through the ducts, entering your house through the vents.
With that explanation in mind, it’s easy to see how a faulty ignitor can cause significant problems. If the ignitor doesn’t create a spark, then there’s nothing to light the gas and start the flame. No flame means no heat in the exchanger, so the blower fan is just going to push cold air through the vents. Luckily, modern furnaces have safety features that will switch off the gas if there’s no ignition detected, preventing a leak, but you’ll still be stuck with a cold house and no way to warm it up.
Types of Furnace Glow Plugs
There are a few different common types of ignitors, and the best way to fix a faulty one will depend in part on which kind you have. For the most part, they’re split into three different categories.
Standing Ignitor
These ignitors are the classic pilot lights of days gone by. They’re much less popular than they used to be, but plenty of older furnaces still have standing pilot lights. These ignitors consist of a small burner connected to a gas line. Once you light the flame, the gas keeps flowing through the line, keeping the pilot light lit all the time. Pilot lights also come with sensors called thermocouples that act as safety features. If the thermocouple detects that the pilot light has gone out, it automatically closes the valve to the gas, preventing any from leaking out. Old-school pilot light ignitors are still a fairly reliable way to start a furnace, but they’re much less energy efficient since they stay lit 24/7. The steady flow of gas also makes them a little riskier – if the thermocouple fails, there’s nothing stopping the gas if the light blows out.
Intermittent Ignitors
These ignitors were invented to fix the major problems posed by pilot lights: wasting fuel, and the light blowing out. Rather than using an actual flame, intermittent ignitors are electrical in nature and end with an electrode inside the ignition chamber. When the thermostat sends a signal to turn on the furnace, electricity flows through the ignitor and creates a spark, igniting the gas in the chamber and lighting the burners. The ignitor then switches back off, saving electricity. Most modern furnaces are equipped with these.
Heating Element Ignitors
Another common form of electrical ignitor, these parts use heating elements similar to the filament wires found in lightbulbs. When electricity flows into the ignitor, it eventually heats up enough to ignite the fuel, a little bit like the old cigarette lighters that used to come in cars. These ignitors are also sometimes called glow plugs because the flow of electricity causes the heating element to glow. Glow plugs also avoid major problems with pilot lights, but they tend to burn out after a few years and need to be replaced.
Warning Signs of a Faulty Ignitor
Most of us don’t pay especially close attention to our HVAC systems throughout the day, so it can be hard to notice if something is going wrong. You likely won’t be able to tell that your ignitor has a problem until it suddenly stops working. The sooner you realize there’s a problem, the sooner you can get someone out to fix it, so here are a few warning signs that you should pay attention to:
Cold Air Through the Vents
If your furnace is on but the air coming through the vents isn’t warm, then the problem could be with the ignitor. When the ignitor fails, the blower fan will sometimes keep working and just blow room-temperature air through the ducts. If you notice that the air coming out of the vents is the same temperature as the air in the room, the first thing you should do is check your thermostat. If it’s accidentally been set to COLD or FAN instead of HEAT, then it’s just not sending the signal to switch on the ignitor. It’s also worth double-checking to make sure that the thermostat is set to the temperature it’s supposed to be.
Furnace Won’t Turn On
If the house keeps getting colder but the furnace never actually switches on, the ignitor could be to blame. Perform the same thermostat checks from the last section before checking out the furnace itself. It’s also worth checking the breakers to make sure that the unit is actually receiving the electricity it’s supposed to. If the breaker is switched to “on,” then there’s likely an electrical problem with the ignitor or elsewhere in the furnace. Some safety features prevent the ignitor from sparking if something goes wrong, so the problem could also be elsewhere.
Furnace Stops Blowing Suddenly
If the furnace suddenly switches off and refuses to turn back on, then there’s a good chance that something has tripped one of the unit’s safety features. This could be the ignitor, but it could also be something else. Start by checking the air filter in the furnace. If there’s debris blocking air from flowing through the filter, that can cause the furnace to switch off. Clean or replace the filter and wait to see if the unit turns back on. If that doesn’t work, the problem might be with the ignitor.
Furnace Starts and Stops Repeatedly
Normally, the furnace should stay on long enough to raise the temperature in the whole house and stay off for at least a little while after. If the unit is constantly turning on and off rapidly, that’s called short cycling and it’s a symptom of a greater issue. Short cycling is extremely bad for the parts inside the furnace, so you should switch it off until you can get it looked at. If you have a glow plug, sudden short cycling could be an indication that the part is on its way out and can’t hold a charge long enough to heat the air.
Repeatedly Tripping the Breaker
Furnaces require a lot of electricity, so it’s not necessarily a problem if they trip the breaker every now and again. However, if you notice it happening frequently, then there’s probably something wrong with the electrical system. If you have an intermittent ignitor, sometimes faulty wiring can cause a short every time the furnace tries to switch on. Pay attention to when the breaker is tripped. If it happens shortly after the furnace turns on, then there’s a good chance that the ignitor is causing the problem. This can be pretty bad for the unit, so leave it off until you can get it fixed.
Ignitor Clicks But Nothing Happens
If you hear the sound of the ignitor clicking on but the air never actually starts blowing, that could be a problem with the blower fan. It could also be a dangerous issue with the ignitor, however, so make sure you keep the furnace switched off. If the unit turns off shortly after the ignitor clicks, that could mean that something is setting off one of the safety features and shutting down the furnace.
Causes of a Faulty Ignitor
There are plenty of reasons why an ignitor might fail, and not all of them require you to replace it with a new one. Here are a few problems that can cause a furnace ignitor to act up, plus some tips on how you can potentially fix the issue:
Dirty or Broken Flame Sensor
All modern furnaces come equipped with flame sensors as vital safety features. These sensors control the gas valve and only release fuel into the chamber if they detect that the ignitor is working properly. In old furnaces with pilot lights, the thermocouple served this purpose, but modern sensors are more advanced. Because a non-functional furnace is significantly better than one that explodes and burns your house down, flame sensors tend to err on the side of caution. If there’s anything wrong at all, including with the sensor itself, it will shut down the gas and refuse to let the furnace operate.
If your furnace hasn’t been properly cleaned and maintained, the flame sensor can sometimes become caked in grease or other debris. This prevents the sensor from detecting the ignitor even if it’s working properly, causing it to think there’s a problem. Simply cleaning the flame sensor can sometimes be enough to get your furnace up and running again. If you don’t feel comfortable cleaning the sensor by yourself, feel free to call a professional to do it for you.
Electrical Short Circuit
Furnace ignitors usually take in a standard 120-volt electrical supply from a household outlet. This provides just enough power to create a spark or heat up a glow plug, but any fluctuation from that range can cause a problem. A power surge can cause the ignitor to short-circuit or flip the breaker. If this happens, just switch the breaker back on and try again. If it ends up being flipped again, the safest option is to just leave the furnace off and wait until someone can take a look at the electrical system.
Dirt or Dust on the Ignitor
Much like the flame sensor, if dust or dirt covers the ignitor then it won’t be able to work properly. Gunk on the ignitor can block the electrodes that cause the spark, and it can also trap heat to prevent a glow plug from igniting the gas. Dirt is actually one of the most common culprits for furnace problems because it can enter through the air filter and settle on the parts inside. The best way to avoid this problem is to be diligent about changing or cleaning the air filters as frequently as the manufacturer recommends. Dust can also enter the furnace through the ducts if they’re not clean. We recommend having your ducts cleaned about once every two to five years for this reason. If you do have dirt or grime covering the ignitor, we actually don’t recommend trying to clean it yourself. Those parts can be extremely delicate and even the smallest mistake can leave you needing a replacement.
Low Gas Pressure
Sometimes the problem with your ignitor doesn’t lie with the ignitor at all but with some other part. Your furnace requires two things to start up: a light from the ignitor, and fuel to burn. Sometimes a faulty valve or other problem with the gas line can cause the pressure to be low, preventing enough fuel from reaching the chamber. Without fuel, the ignitor can spark over and over again without creating any heat for your house. This can sometimes appear to be an ignitor issue, but closer inspection reveals that the gas line was the culprit all along.
A problem with the gas line in your furnace can be a dangerous thing, so we don’t recommend messing around with it by yourself. If your furnace isn’t working properly, make sure you leave it off until a professional can take a look at it. Allowing the furnace to keep running while it’s malfunctioning can make things a lot worse, and a problem with the gas line can turn into a leak if you’re not careful. If you want to be extra cautious, you can manually shut off the valve connecting the furnace to the gas main, ensuring that nothing leaks into your home.
Glow Plug Needs to Be Replaced
Even if you take great care of your furnace, a glow plug will eventually burn out from regular use. As a general rule, you can expect to get about seven years out of a heating element ignitor before you have to replace it with a new one. If the glow plug dies, you won’t be able to use your furnace at all until you purchase a replacement. Luckily, the cost of a new glow plug isn’t too expensive, so you won’t have to break the bank to get your HVAC system up and running again.
Checking the Ignitor
While we recommend hiring a professional to help you fix any problems you might have with your ignitor, you might feel confident enough to replace it by yourself if you have experience with HVAC systems. It can also be helpful to know how to check the ignitor so you can diagnose a problem before calling an HVAC technician. Knowing what the problem is can make their job a lot faster and easier, saving you time and maybe even a little money.
Before accessing the ignitor, you’ll have to do a few things for safety purposes. First, make sure you unplug the furnace from the wall so you don’t get shocked. You can also switch off the breaker for the furnace, either way will prevent electricity from flowing into the unit. Next, turn off the gas valve that leads into the furnace from the gas main. You don’t want to have to worry about any gas escaping accidentally while you’re poking around in there. Finally, wait a few minutes before you actually open the furnace up. The metal pieces inside can retain heat even after the furnace has been shut off, so you’ll want to wait until you’re sure you won’t burn yourself.
Once you’re ready, you can open up the service panel located on the side of the furnace. Some access panels are held in place by screws that you’ll have to remove, but others just have hinges and a latch of some kind. Once you’ve opened up the panel, look for the ignitor among the electrical wires not far from the gas hook-up. If you have an intermittent ignitor, look for the two small metal prongs that create the spark. If you have a glow plug, look for a white ceramic base with a flat metal surface above it.
Finding Furnace Repair in Santa Rosa
A faulty ignitor can be a tricky thing for most homeowners to fix by themselves. The parts involved tend to be fairly delicate, and it’s easy to accidentally make a mistake and break something. They also need to be installed very carefully. Making a mistake when dealing with the inner workings of a furnace can create a safety hazard, allowing natural gas to leak into your house or even letting the combustion process create carbon monoxide. As a general rule, we recommend that you let a professional HVAC technician handle this work for you.
If you’re in Marin, Sonoma, or Napa County, then Valley Comfort Heating & Air is here to help you with anything you might need, including servicing your furnace and inspecting the ignitor. You can get in touch with us through our website here, by visiting us at our physical location in Santa Rosa, or by giving us a call at (707) 539-4533.