A person drawing a blanket close to them because they are cold.

What To Do When Your Furnace Is Blowing Cold Air

Has your furnace been blowing cold air and you just can’t figure out why? Are you confused about why your house isn’t as warm as you want it to be? Well, there could be a number of reasons why your central heat is blowing cold air. We’ve compiled a list of some of the most common issues that may be causing your furnace to act up, as well as things you can do to fix it!

Just as a disclaimer, it can never hurt to get a professional to look at these sorts of issues, especially if you feel that you may put yourself at risk by trying to determine or solve the issue. In that case, give us a call! However, there are often some pretty common problems that furnaces have, as well as simple ways to fix them on your own.

Common reasons your furnace is blowing cold air (and what to do about it)

The pilot light is out

A pilot light is pretty common in older furnaces. If you don’t know what a pilot light is, it’s a small flame that runs at all times in order to light the burners in your furnace. However, many furnaces have newer and more efficient ways of lighting. An electric ignitor does not require any pilot light and acts very similar to a gas stovetop. This type of furnace simply creates a spark and this spark lights the burners, saving the pilot light from being on at all times.

Sometimes, a pilot light might go out simply because of a strong gust of air. If you’re knowledgeable and comfortable doing it, you can try to relight the pilot yourself. If not, call a professional – we can help! And if relighting the pilot light doesn’t fix the problem, there may be larger issues that require replacement of the furnace.

Inadequate gas supply

In relation to the previous issue about the pilot light, a lack of gas supply could be the reason for the pilot light to be out. In this case, make sure the gas supply is turned on and that the pipe is properly in position and attached to the furnace.

Sometimes, there can even be too much grime or dirt around the connection where the gas helps to light the pilot light. This could simply be fixed by having the system professionally cleaned. 

Check the thermostat

If the thermostat is the issue, there is often no need for any repairs. Do you sometimes notice that your furnace is only blowing cold air on occasion? Is your home still maintaining its temperature? This could simply be a thermostat issue.

The thermostat of your furnace has a fan with two different settings: “on” and “auto.” The “on” setting means that the furnace fan will be running even when the furnace itself is off. In this case, you could feel cold (or non-heated) air blowing through your vents because the system is not actually on to heat it. This air might not always be cold, and could be room temperature as well.

One way to fix this issue is by turning your setting to “auto.” In this case, the furnace fan will turn on automatically when your home’s thermostat recognizes that the house is at a different temperature than what it’s been set to. This will then cause your furnace to start heating up while the fan starts to circulate the hot air.

There may be other issues in relation to the thermostat, especially if you installed it yourself. Not every thermostat is compatible with every heating system. You might want to consider consulting an HVAC expert for advice. Also, if you’ve had the thermostat for a while, the batteries could simply be running low and in need of a change.

Condensate clog

Another common issue amongst newer furnaces is a condensate clog. These newer and more advanced furnaces have what is called a condensate drain. This drain removes and drains water that is created in the heating process. When this drain becomes clogged, it can prevent your furnace burners from lighting. Again, if you feel comfortable, trying unclogging the drain, and if not, make sure to contact a professional. 

Clogged filter causing safety control to shut off

Furnace filters are pretty easy to forget about, but they should be one part of the furnace that is checked on every few months. Dependent on your lifestyle, like how much time you’re spending at home, if you are doing construction or improvements in your home, etc., you may feel the need to change this filter more often. The more contaminants that are floating through the air, the more your filter will have to clean.

A clogged filter will cause your furnace to work harder to push hot air throughout your home and can increase the likelihood of a costly furnace repair. Again, a simple fix is to just make sure that you are checking and changing your filter as often as necessary for your needs.

If your furnace starts to overheat, your furnace may cause the limiter switch to go off. This is a safety feature that turns off the burners to prevent a fire in your home. It’s important not to overlook this issue, as it can cause damage to your furnace’s heat exchanger, which can be a costly repair.

Overheating almost always occurs due to restricted airflow as a result of a dirty filter. A lack of airflow means that the system needs to run a lot longer and harder in order to provide adequate heat. This will then cause the system to overheat, causing much larger issues. Frequent overheating will likely cause damage to your heat exchanger, requiring a costly replacement. Simply prevent this issue by making sure that your filter is changed regularly and stays fairly clean! Once changed, always check to make sure that your heater is blowing warm air only. 

High-efficiency vent pipes are blocked

On newer and more efficient furnaces, there are typically vent pipes that lead from the furnace to the outside of your home. There are usually PVC pipes and, again, can sometimes get clogged or blocked. This can often get blocked by simple forms of debris, or larger issues like ice, causing your entire system to shut down. Obviously, the best way to solve this problem is to find the root cause and eliminate it. If the issue is ongoing, for example, if ice or snow has a tendency to pile up where the pipes lead to the outside of your house, consider bringing in a professional to move this piping to a more convenient place. 

Leaking ducts

Sometimes ducts may leak, causing air from colder places, like your basement or attic, to get into your vents. This can contribute to cooler air flowing from your vents and through your heating system. This also means that the hot air from your furnace is escaping through holes in the ducts. Have an expert inspect your ducts, as well as the furnace. 

Issues with controls

Many newer furnaces are hooked up to electric control panels. Sometimes all you need to do to fix this problem is just to reset the system! You could try turning the furnace off via the power switch. It might be best to wait a few minutes and then try turning it on again. Just like rebooting your computer, sometimes the system just needs a restart. If the furnace still blows cold air, then you may need a professional to take a look. 

Compromised flame sensor

Does your furnace start by blowing warm air, but then quickly turns cold? The flame sensor on the furnace may need attention. A flame sensor that is covered in grime or debris, or is simply worn out, can cause the burner to continually be shutting off. You’ll need a visit from an HVAC professional to help fix this furnace issue. 

Helpful tips and preventing future repairs

Overall, one of the best things to keep in mind with your furnace is to regularly check on it and perform the necessary regular maintenance. Many issues can be prevented simply by regularly cleaning to prevent grime, debris, and clogging, some of the most common problems that are found in problematic furnaces!

If you haven’t given your furnace a check in a while, or even changed the filter in the last couple of months, now is the time! With winter just around the corner, you do not want to be caught with a faulty furnace and a cold house. 

Finally, don’t hesitate to call in a professional! It’s always better to be safe than sorry, especially if you don’t feel comfortable fixing, or even checking for, issues regarding your central heating system. We’d love to take the load off and help you as much as we can, so don’t hesitate to give us a call!