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Reasons Your Furnace Is Blowing Cold Air


Investing in a good quality furnace can last 15 to 20 years with the correct maintenance checks and inspections. But, sometimes problems can arise.

Several furnace problems can lead to cold air issues, so you must learn what to look for and schedule a furnace repair as soon as possible. Before you panic and start getting worried about your broken furnace, you should check the unit and inspect the issue. Then, you can call a professional to come and take a look.

Here is your guide to identifying why your furnace is blowing cold air.

  • Your pilot light may be damaged.
  • The flame detector could be dirty.
  • The furnace air filter could be blocking air flow.
  • The home could have a low gas supply.
  • The condensate lines could be blocked.
  • Ductwork for the furnace could be damaged.
  • The thermoset could be incorrectly set.

The Pilot Light Is Damaged

The pilot light is the first thing to check when your furnace is blowing cold air. This is the feature that ensures your burners are working and it produces heat. So, if this is not working, then you might be feeling cold air.

The Flame Detector Is Dirty

Some other possible causes of cold air coming from a furnace are that there’s dirt and debris on the flame detector. Several designs rely on flame detectors to heat the furnace.
If this is the case, you’ll need to check the feature and ensure no dirt and grime are blocking the detector. You can fix this problem quickly by cleaning the flame sensor on the furnace.

A burner in a gas furnace

Blocked Air Filter

A blocked air filter can also restrict airflow in the furnace, leading to cold air coming from the unit. The air filter is crucial for keeping fresh, clean air around your furnace.
Therefore, if this part becomes blocked by dust, it can lead to temperature issues. You can spot problems with blocked air when the furnace experiences overheating or long heating cycles.
Try replacing the air filter, as this should be able to get rid of the blockage and improve the quality again.

A King technician displays a dirty HVAC air filter (right) side-by-side with a clean HVAC air filter (left).

Low Gas Supply

Gas can contribute to complications with home furnaces, especially if a house has a low gas supply. Most furnaces are designed to shut off when there’s not enough gas supply.

Even though this is the primary safety feature, it can indicate other issues and lead to cold air flowing through your space. If there is a problem with your gas supply, you need to call a professional.
You should never attempt to do this alone. It’s best to let a professional take care of it for you.

Condensate Lines Aren’t Working

Condensate lines are included in furnaces to help with removing excess moisture. Like air filters, this feature can become blocked quickly if the furnace is old or hasn’t been inspected for several years. You can keep an eye on your condensate lines with regular maintenance checks, as this will allow you to stop problems developing in this area.

Ductwork Is Damaged

If your ductwork is damaged or has become disconnected in a crawlspace or attic it can lead to heat loss through the ducts. Check to make sure that the ducts are properly connected to the registers.

The Thermostat Is Incorrectly Set

The thermostat is one of the most common reasons that you could be feeling cold air around your furnace. You should check the thermostat to ensure it’s set to heating or auto.
Sometimes the thermostat can be incorrectly set.

Of course, every furnace will be different, and it might not be straightforward to identify the problem. You don’t need to sort the issue yourself; you can call our team to help you fix the furnace.

How to extend the lifespan of furnaces

Call Us When Your Furnace Is Blowing Cold Air

It can be uncomfortable and frustrating when your furnace is blowing cold air. Our team at King HVAC is here to help.
Although the problem might be small, it’s best to get a professional to come and inspect the unit. This will save you money in the future and ensure you won’t have any further issues with your furnace.
Plus, you can also use our services for your future maintenance checks.
Get in contact and talk to the team to book an appointment today.