Why Is My Furnace Not Turning On?
Why Is My Furnace Not Turning On | Causes and Fixes
If your furnace is refusing to turn on, it could be from something as simple as an incorrect thermostat setting or a tripped breaker. It could also be from something more substantial, like a faulty ignition system or a damaged control board.
Remember: If you smell gas, hear it escaping, or suspect a gas leak, stop troubleshooting immediately. Leave your home without touching any electrical switches or devices, get to a safe location, and then call 911 or your gas company.
Why can a furnace fail to start?
Your furnace has to complete several steps before it can begin sending warm air throughout your home. The thermostat first signals that heat is needed, followed by a series of airflow, venting and ignition checks. So if something interferes with one of the steps, it may shut down shortly after it turns on or not even start in the first place.
Keep in mind that while a short pause at startup is usually normal, repeated clicking, unsuccessful ignition attempts, or a furnace that starts and quickly turns off could indicate that something is preventing the cycle from continuing.
Thermostat settings
The thermostat is responsible for telling your furnace when the home needs more heat. If the indoor temperature drops below the selected setting, it sends a signal to your furnace to begin heating up your home.
There are a few things that can prevent that signal from reaching the furnace, including:
-
Dead batteries
-
Incorrect programming
-
A faulty thermostat
Airflow and safety
If a clogged air filter or blocked vent limits a furnace's airflow, it can cause heat to build up inside the system. This can trigger a safety shut-off if it gets too hot.
Other safety controls can also stop the system from starting. For example, if the blower door is not seated correctly, or there is a problem with the venting or condensate drainage.
Ignition and flame sensors
It's more common these days to find an electronic ignitor in modern furnaces than a pilot light. A furnace ignitor can eventually crack or stop working over time. If that happens, the burners would be unable to ignite.
In a natural gas furnace, the flame sensor confirms that a flame is present and the gas is burning properly once the burners are lit. If the sensor is too dirty to detect the flame, or if it's no longer working the way it should, the furnace may shut off the gas supply and turn the burners back off.
Quick DIY furnace checks you can do in five minutes
Before you book a service appointment, try checking to see if a simple thermostat, power supply or airflow issue is preventing your furnace from starting.
Just remember not to open any secured panels or handle gas lines, electrical wiring, or internal furnace parts. Also, anything that involves gas, electrical wiring or internal furnace components should always be left to a licensed HVAC professional.
|
Check |
What to do |
|
Check the thermostat |
Confirm it is set to 'heat mode' and the fan is set to 'Auto'. Raise the thermostat setting by 2°C or 3°C and wait for the furnace to start. Also, replace batteries if needed and review the programmed schedule. |
|
Replace the furnace filter |
Turn the furnace off, then replace the air filter with the correct size and type. Ensure the airflow arrow is facing the proper direction and that vents are open and unobstructed. |
|
Confirm the furnace has power |
Make sure the furnace power switch is set to 'on'. Also check the electrical panel for a tripped breaker or blown fuse. You can reset the breaker once if needed, but if it trips again, leave it off and contact a certified technician. |
|
Check that the blower door is secure |
Many furnaces have a safety switch that prevents the system from running when the blower door is loose or improperly installed. |
|
Clear the intake and exhaust |
Check the exterior pipes and remove any loose snow, ice, leaves or other debris from around the openings. If a blockage does not come away easily, contact a technician to remove it. |
Why should you address furnace problems early?
A furnace that repeatedly fails to start should not be ignored, even if resetting the thermostat or circuit breaker restores the heat temporarily. The same problem may return during colder weather, when your heating system needs to run more often.
Repairing the source of the issue can help restore proper ignition, airflow and temperature control before a small problem becomes more disruptive.
Cut costs and reduce headaches
A timely furnace repair may help you:
-
Restore steady heat throughout your home
-
Avoid repeated no-heat calls during the coldest weeks of winter
-
Reduce unnecessary wear on ignitors, sensors, motors and electrical controls
-
Improve system performance when airflow or faulty components are affecting operation
-
Identify venting, gas supply or electrical problems before they worsen
When should you repair or replace a furnace that will not start?
A replacement may be worth considering if the furnace is older, repairs are becoming more frequent, it has problems with the heat exchanger, blower motor or control board, or the cost of fixing a major component is adding up.
|
Option |
Best for |
Benefit |
Trade-off |
|
Repair |
One failed part on an otherwise reliable furnace |
Restores heat without replacing the system |
Another aging part may need attention later |
|
Tune-up |
A working furnace with airflow or maintenance concerns |
Provides cleaning, testing and adjustments |
Will not correct a failed major component |
|
Replace |
An older furnace with repeated failures or a costly repair |
Provides new equipment and warranty coverage |
Requires a larger upfront investment |
If both repair and replacement make sense, ask for pricing for each option so you can compare the costs. A repair may be enough to restore your heat, while a new furnace installation may make more sense if your current system is older or has repeated problems.
You may also want to ask whether a heat pump could work for your home. Depending on your heating needs, it may be able to replace your furnace or operate alongside it as part of a dual-fuel system.
How can you prevent your furnace from failing next winter?
While not every furnace problem can be prevented, regular maintenance is one of the best ways homeowners can prevent their furnace from failing next winter. Here's what you should aim to do before the next heating season:
-
Check the air filter and replace it when needed, following the furnace manufacturer’s instructions
-
Book annual maintenance before you begin using the furnace regularly
-
Make sure the intake and exhaust pipes are clear of snow, ice and other debris
-
Review the thermostat settings, programmed schedule and batteries
-
Make sure furniture, rugs and other items are not blocking the supply registers or return vents
-
Have a technician take a closer look if your furnace begins making strange noises, turning on and off too often, struggling to ignite or showing recurring error codes
Already noticing signs that something is wrong? Contact Enbridge Sustain to book a furnace diagnostic or request a repair quote.
