There’s nothing quite like that sinking feeling when your furnace fails to start, especially during a cold snap in Calgary, when the temperature outside could freeze your coffee in minutes. Don’t panic just yet. Many ignition problems have straightforward causes that can be safely checked before calling a technician.
In this guide, we’ll walk through what causes furnace ignition failures, what you can troubleshoot on your own, and when it’s time to call the pros at Comfort Union for help.
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Why Does Gas Furnace Ignition Fail?
When your furnace refuses to ignite, it means something is preventing the burners from lighting or staying lit. The ignition process involves three key parts: a pilot or ignitor, a steady gas flow, and a flame sensor that verifies the flame is present. If any part of this system malfunctions, your furnace’s safety controls will stop it from firing to prevent gas buildup or overheating.
An ignition failure isn’t just an inconvenience. It can lead to your home losing heat, increase wear on furnace components, and, in some cases, pose safety risks. In Calgary’s long, dry winters, where furnaces run nearly nonstop, even a small ignition issue can quickly turn into a no-heat emergency.
7 Causes Your Furnace Won’t Ignite (and What They Mean)
Let’s break down the most common reasons Calgary homeowners face ignition trouble and what each one might indicate.
1. Thermostat or Control Issues
Your furnace depends on clear communication from the thermostat. If it’s set incorrectly or malfunctions, it may not tell your furnace to turn on at all. Make sure the thermostat is set to “Heat” and that the temperature is higher than your home’s current temperature.
If that checks out, the problem might be a wiring issue, dead batteries, or a control board failure. A professional can test these safely and recalibrate your system if needed.
2. Insufficient Gas Supply or Closed Gas Valve
If the gas valve is partially closed or the line is blocked, your furnace will power up but won’t ignite. You might even hear it try to start before shutting down.
Ensure your gas valve handle is parallel to the pipe, which means it’s open. If you’re using propane, confirm your tank isn’t empty. For natural gas systems, check with your provider (such as ATCO Gas) if there are any outages in your area. Never try to repair or disassemble gas lines yourself, since this requires a certified technician.
3. Dirty or Faulty Ignitor or Flame Sensor
Over time, soot, corrosion, or dust can coat your ignitor or flame sensor. When this happens, your furnace might light briefly and then shut off immediately.
If your system has a glow ignitor, it should glow bright orange before ignition. If it doesn’t, it might be burned out or misaligned. Similarly, a dirty flame sensor can’t detect a flame and will cut off gas flow for safety. These are affordable parts to replace during your next furnace tune-up.
4. Clogged Burners or Blocked Orifices
Just like Calgary’s roads in January, your furnace burners can get clogged with dirt and debris over time. When that happens, the fuel-air mix is disrupted, and the burners won’t ignite properly.
You might notice your furnace clicking but not firing up, or the flame sputtering and going out. Cleaning the burners typically solves the problem, but since it involves handling gas components, it’s best left to a professional technician.
5. Faulty Gas Valve or Solenoid
The gas valve controls how much fuel flows to your furnace burners. If it sticks closed or the solenoid fails electrically, your furnace won’t ignite at all.
Common symptoms include repeated clicking sounds without ignition or no flame, even though the blower fan runs. Replacing a faulty gas valve is a precise job that requires pressure testing and proper calibration, so this is another situation for a licensed HVAC professional.
6. Overheating or Airflow Interruption
When your furnace overheats, a high-limit switch shuts the system off as a safety precaution. It may start the blower to cool things down, but the burners won’t relight until the system resets.
Overheating often happens when airflow is restricted by a dirty filter, closed vents, or blocked return ducts. Calgary’s dry air can also cause dust buildup that worsens this issue. Changing your filter every 1–3 months and keeping vents open can prevent this type of shutdown.
7. Electrical or Power Issues
If your furnace isn’t getting power, it can’t ignite. Check your breaker panel to make sure no circuits have tripped. Also, inspect nearby outlets because sometimes furnaces share power with other appliances that may have shorted out.
Low voltage or surge damage can also affect your ignition control board. If you’ve had recent electrical storms or power flickers, the control module might need replacement or resetting by a technician.
Safe Checks You Can Do Before Calling for Repair
Before booking a service appointment, you can safely check a few basics yourself:
Confirm the thermostat is set to “Heat” and functioning properly.
Make sure the gas valve is fully open.
Inspect your furnace filter and replace it if dirty.
Check your breaker panel for tripped switches or blown fuses.
If your furnace has a reset switch, press it once and see if the unit reignites.
If the furnace still won’t light after these steps, it’s best to call in a professional rather than risk further damage or safety issues.
When to Contact a Calgary Furnace Technician
If your furnace is repeatedly trying and failing to ignite, it’s time to get expert help. Call Comfort Union right away if you notice:
If your furnace keeps trying and failing to ignite, it’s a clear sign that professional attention is needed. Call Comfort Union right away if you notice any warning signs, such as a gas or burning smell coming from your unit, clicking or popping sounds during ignition attempts, or continuous cycling without producing heat. Another red flag is a flickering or yellow pilot flame, which could indicate a combustion or ventilation problem. Getting expert help quickly ensures your system is repaired safely and prevents further damage or safety risks.
Our Calgary technicians are trained to diagnose ignition failures quickly and safely. Whether it’s a worn ignitor, faulty valve, or airflow issue, we’ll get your heat back on and your home comfortable again. You can also learn more about professional furnace repair services in Calgary.
How to Prevent Future Ignition Failures
Keeping your furnace in top shape year-round helps avoid the stress of a no-heat night.
- Schedule annual maintenance before winter to catch ignition issues early.
- Clean or replace filters regularly to maintain proper airflow.
- Have sensors and ignitors checked every few years to prevent buildup.
- Inspect ductwork and vents to avoid airflow restrictions.
- Test your gas line and regulator for proper pressure and operation.
A little maintenance goes a long way toward preventing sudden breakdowns during Calgary’s coldest weeks.
FAQs Calgary Homeowners Ask About Furnace Ignition Issues
Why does my furnace click but never ignite?
That usually means your ignitor or gas valve isn’t working properly. It’s best to have it tested by a licensed technician.
Can a dirty flame sensor stop my furnace from starting?
Yes. A dirty sensor can’t detect the flame, causing your system to shut off immediately for safety. Cleaning or replacing it usually solves the issue.
What role does the gas valve play in ignition failure?
The gas valve regulates fuel flow. If it’s stuck or electrically faulty, your furnace won’t ignite because it can’t release gas to the burners.
Is it safe to keep trying to start a furnace that won’t ignite?
No. If your furnace fails to start after one or two attempts, turn it off and call a professional. Repeated ignition attempts can lead to gas buildup or damage.
Final Thoughts
When your furnace refuses to ignite in the middle of a Calgary cold spell, it’s tempting to panic, but the solution is often straightforward. Whether it’s a sensor, ignitor, or airflow issue, most problems can be resolved quickly by a professional.
If your furnace still won’t start after basic troubleshooting, contact Comfort Union for a quick diagnosis and reliable repair.
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