It's usually on the coldest night of the year that your armstrong furnace ignitor decides to give up the ghost, leaving you shivering in your favorite thick hoodie while you wonder why the vents are blowing cold air. It is a frustrating situation, but honestly, it's one of the most common issues homeowners face with their heating systems. These little components do a lot of heavy lifting, and like a lightbulb, they eventually just burn out after too many cycles.
The good news is that you don't necessarily need to be an HVAC expert to figure out what's going on. If you're even a little bit handy with a screwdriver, you can often diagnose and fix this yourself without waiting three days for a technician to show up and charge you a small fortune for a twenty-minute job.
Signs Your Ignitor Is on Its Last Legs
You'll usually know something is wrong when you hear the furnace kick on, the inducer motor starts humming, but then nothing. No "whoosh" of flames, no heat, just a click and then the system shuts back down. If your furnace tries to light three times and then goes into a "lockout" mode, your armstrong furnace ignitor is the prime suspect.
One of the easiest ways to tell if it's dead is just to watch it. Most Armstrong units have a little peep hole or a removable panel. When the furnace starts its cycle, that ignitor should start glowing a bright, orange-white color. If the rest of the furnace is doing its thing but that part stays dark and cold, it's toast. Sometimes you can even see a physical crack on the element itself, almost like a burnt-out filament in an old-school incandescent bulb.
Why These Things Burn Out Anyway
You might be wondering why a piece of your furnace just decides to quit. These ignitors are usually made of silicon carbide or silicon nitride. They get incredibly hot—hot enough to ignite natural gas or propane instantly—and then they cool back down to room temperature. This constant expansion and contraction eventually causes the material to fatigue.
Over time, dust can also build up on the element. If a speck of dust or some moisture gets on it, it creates a "hot spot" that makes the material brittle. Also, if you've ever had a professional (or a well-meaning DIYer) touch the element with their bare fingers, the oils from their skin can actually cause the ignitor to crack the next time it heats up. It sounds a bit dramatic, but these things are incredibly sensitive.
Testing Your Armstrong Furnace Ignitor
If you want to be 100% sure before you go out and buy a replacement, you can test it with a basic multimeter. First, make sure you've turned off the power to the furnace—you don't want to get a surprise shock while you're poking around.
Locate the wires leading to the ignitor and unplug the plastic harness. Set your multimeter to the lowest Ohms setting (resistance). Stick the probes into the plug holes on the ignitor side. If the meter shows "OL" (open loop) or an infinite reading, the internal circuit is broken, and the part is definitely dead. A healthy armstrong furnace ignitor should typically show a resistance reading somewhere between 40 and 90 Ohms, though this can vary depending on the specific model you have.
How to Swap It Out Yourself
Replacing the ignitor is pretty straightforward. Once you've confirmed the power is off and the gas is shut off (just to be extra safe), you'll need to remove the burner cover if your model has one. Usually, the ignitor is held in place by a single screw or a small metal bracket.
Carefully unscrew it, but be mindful not to drop the screw into the dark abyss of the furnace cabinet—finding a tiny screw in there is a nightmare you don't want. Gently pull the old ignitor out. It's a good idea to take a photo of how it was positioned before you remove it, just so you know exactly how the new one should sit.
When you take the new armstrong furnace ignitor out of the box, handle it like a fragile egg. Do not touch the gray or black element part with your fingers. Hold it by the porcelain base or the plastic plug. If you do accidentally touch it, wipe it down gently with some rubbing alcohol and let it dry before installing it. Slide it into place, tighten the screw (don't over-tighten, or you might crack the porcelain), and plug it back into the wiring harness.
Choosing the Right Replacement Part
When you're looking for a replacement, you'll see a lot of options. You can get the official OEM (Original Equipment Manufacturer) part from Armstrong, or you can find "universal" ignitors that claim to work for everything.
While the universal ones are often cheaper, they don't always fit perfectly in the bracket. If the ignitor isn't positioned exactly where the gas flow is strongest, the furnace might struggle to light, which leads to "delayed ignition"—that's when you hear a loud bang when the furnace finally catches. It's usually worth the extra ten or fifteen bucks to get the exact match for your Armstrong model number. It just saves a lot of headaches during the installation.
Recently, many people have been switching from the older silicon carbide ignitors to silicon nitride versions. The nitride ones are way more durable and less likely to break if you accidentally bump them. If your furnace allows for the upgrade, it's a smart move that might keep you from having to do this again in three years.
A Few Rookie Mistakes to Avoid
The biggest mistake people make is skipping the "turn off the power" step. Even if the furnace isn't running, there's still electricity sitting at those terminals. Another common fail is not checking the furnace filter while you're in there. If your filter is clogged, it can cause the furnace to overheat and cycle more often, which wears out the armstrong furnace ignitor much faster than normal.
Also, don't assume it's the ignitor without checking your circuit breaker first. It sounds silly, but people have spent hours taking their furnace apart only to realize a breaker tripped or the service switch on the side of the furnace was accidentally bumped to "off."
When Should You Call a Pro?
If you replace the ignitor and the furnace still won't light, or if you see the ignitor glowing but the gas isn't catching, you might have a different problem. It could be a faulty gas valve, a clogged burner orifice, or a bad control board.
At that point, unless you're really comfortable digging into the gas train and electrical diagnostics, it might be time to call in a technician. There's no shame in it—sometimes the problem is deeper than just a simple plug-and-play part. But in the vast majority of "no heat" cases with these units, a fresh armstrong furnace ignitor is exactly what the doctor ordered.
Once you've got the new one in and you see that bright glow followed by the roar of the burners, you can finally kick back, relax, and enjoy the warmth. It's a great feeling of accomplishment to fix your own heat, and your wallet will definitely thank you for not calling for emergency service on a weekend!