The Top 10 Causes Of Furnace Failure | Furnace Repair From Action Furnace

Education Centre, Furnaces

Here is a list of the 10 most common problems so you know what to keep an eye out for to prevent damage or total failure.

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Posted by Ryan | November 2, 2023

When the snow is blowing and your furnace gives out, knowing that the failure was likely preventable is a bit of a “cold comfort”. The best way to prevent furnace failure and subsequent freezing is by routinely checking your furnace before the cold season hits each year. If you’ve encountered a furnace problem regardless, look into the list we’ve compiled below to hopefully save some time and money.

1. Malfunctioning Thermostat

Modern digital programmable Thermostat in home set to 24°C during day time

The first thing to check is whether your thermostat is doing its job. First, is it on? And is it on the right setting? Be sure that it is switched to heat. You may think this is obvious, but about a quarter of service calls made could be avoided with this simple check.

2. Switches & Breakers

Secondly, is the furnace unit really the problem? Check your fuse box to see if any fuses have been blown. Be sure that none of your breakers are causing the furnace to malfunction. And check the unit to see if it’s the power switch is on - every furnace has one! It’s also a good idea to check that the front panel door is latched properly - if this door isn’t secure, most furnaces won’t engage.

3. Ignition Failure

If the above suggestions haven’t solved the issue, check to see if the ignition is the problem. If the pilot light or electrical ignition systems are out of sorts, your furnace cannot operate. To check a pilot light, open the burner chamber door and find the pilot light tube. If you do not see a small flame, your pilot light is likely out.

4. Blower Motor

If the blower motor (or fan motor) isn’t working, then the furnace cannot move the heat it is generating through your house. Check if there is an issue with the fan motor, as this could mean your furnace is still working - just not blowing warm air out to where it should

5. Dirty Filters

Close up of dirty filter with hand showing dust and debris between filter folds.

A very common cause of furnaces not working properly is dirty or clogged filters. This could be especially true if you have pets or a large number of people in your household. It is important to regularly change your furnace filters to maintain both your furnace system and your home's air quality.

6. Blocked Ducts or Vents

Dust from duct cleaning lying beside air vent

Another important and common cause of furnace failure is a blockage somewhere in the ventilation or duct system. Having your vents cleaned regularly is an important aspect of home maintenance that increases air quality, energy efficiency, and keeps your furnace running smoothly. Don’t forget to check the air intake or any other passages that move air directly in or out of your home. A variety of debris could be built up in these areas, from leaves and litter to a misplaced toy or wild animal. Be sure to check your chimney/exhaust flue is clear - this could also prevent a house fire.

7. Air Leakage

Professional technician working on AC units in residential home.

Perhaps your furnace is running, the ducts are clear, you’ve checked all the switches, but you’re still not getting the warm air that you should be. It could be that there is an air leak somewhere in your system. If the warm air is heading outside instead of heating the house, your home will be a bit cool. Or, if there is a draft (perhaps one that you cannot feel directly) then too much cold air could be coming in. Complete a thorough check of the interior and exterior of your home to determine if this is the case.

8. Fuel Supply

Whether you have a furnace that’s more dated or a newer high-efficiency model, it can’t do its job without fuel. All furnaces need a fuel supply, though what fuel they use and how they use it can vary. A lot of furnaces in Alberta run on natural gas. However, there are also electric and induction furnaces. If your furnace does run on gas, make sure the lines are working and that the gas valve is turned on.

9. Drainage

If you have a high-efficiency furnace, it’s likely draining off a lot of water throughout the cold season. Check that there is no sediment or mold in the drainage hose, as any restrictions could result in it becoming plugged or blocked. If possible, remove a dirty hose and give it a good flush. This could solve your problem.

10. Lack Of Maintenance/Mechanical Issues

We live in such a busy world that important maintenance to our home can often be overlooked or forgotten. If your furnace is not being checked regularly by a professional, or just isn’t well-maintained, you could run into all kinds of issues that aren’t as run-of-the-mill as the ones outlined above. If you notice any strange sounds or smells coming from the bowels of your home, it could very well be an issue with your furnace. Don’t hesitate to call a professional if you aren’t sure what the problem might be. We are always happy to help where we can, especially when it comes to your family’s comfort. If you’re interested in learning more about furnaces and their functions, we have compiled a handy list of resources. Check out our Education Centre for tips and pointers on all of your HVAC queries. If you are needing further help, give us a call - our furnace tune-up includes replacement of the furnace filter as well as a check-up of the items listed above.

Ryan | General Manager

Ryan is considered one of Calgary's most knowledgeable residential HVAC specialists. Working in the industry for over 12... more

Top 10 Causes of Furnace Failure