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Furnaces | 7 Min.

Why is my furnace blowing cold air? How To Fix?

Written by Nikita Sharma

Winters in Canada can be freezing cold- it is snowy and chilly. In winter, the temperature stays around zero degrees celsius, it may drop as low as -30 to -40 degrees celsius. During this cold weather, the only reliable source of warmth is your furnace.

In winters, what could be worse than walking into your home with a furnace blowing cold air?

Nothing! The last thing you want on cold days is a broken furnace. Hence, it’s important to find out the reasons why your furnace is blowing out cold air and how to fix it.

After reading this article, you will be able to identify why your furnace is blowing cold air and what you can do to fix it.

Why is My Furnace Blowing Cold Air?

Wrong settings on the thermostat

When your furnace is blowing cold air, the first place to check is a thermostat. Maybe, the thermostat is not set right. For example: when the seasons change or you use furnaces after a long time, you forgot to change the settings on the thermostat. Ensure that your thermostat is set on ‘Auto’, and not ‘On’ mode. In the ‘on’ mode, the fan in your furnace will blow even when your furnace itself isn’t working, resulting in cold air. But, when it is set in the ‘Auto’ mode, your furnace and fan will be working at the same time in coordination to keep you warm.

Thermostat installation issues

Another possible reason why your furnace is blowing cold air could be the wrong installation of the thermostat. Many self-install thermostat kits are available in the market, but all are not compatible with your existing furnaces. You may also make a mistake or two while installing, even if you follow all the stated instructions. A low battery of a thermostat can also cause the problem. Contact an HVAC expert to get a look at your thermostat.

Dirty/clogged filters

You may feel your furnace is blowing cold or with no air because a filter is clogged with dirt and debris. A clogged filter not only blocks the passage of warm airflow but also causes overheating of a furnace. Overheating may result in a complete breakdown of your furnace. To keep your furnace in a good working condition, we recommend timely changing or cleaning of filters.

Broken blower fan

A blower fan in a furnace is used to blow air across the heating coils to produce warm air. If it stops working, your furnace may blow no air at all. By setting the thermostat to “fan-only” mode, you can test whether your blower fan is working.
You must be wondering how to do that. Don’t worry! No technical knowledge is required for this. Just turn off the heat, change thermostat settings from “auto” to “on”, and place your hand in front of the air ducts. If you don’t feel any breeze coming forth then your fan is broken. If you have a big problem at your end, call an expert.

Issues with the pilot light

A pilot light is a small blue flame used to light furnace burners. Commonly, it is present in older furnaces. This light helps furnaces in producing heat. Without it, a furnace will not be able to heat the system. It could also be the reason why your furnace is blowing cold air. New furnaces have different ways of lighting, such as electric ignitors. If you have a pilot light, try to reignite the flame using a lighter. Be careful! It’s safer to take professional help with pilot light.

Overheating of the furnace

Overheating can also be the reason why your furnace is blowing cold air instead of hot. On overheating, a safety feature shuts off the furnace to prevent gas leaks or fire explosions. Mechanical failure, dirty filters, excessive usage, etc are the reasons for overheating of a furnace.

Issues with ducts

You may feel your furnace is blowing cold air, but in reality, the problem is with the air ducts. Leaks or breaks in air ducts cause warm air to escape, leaving you cold. It is difficult to locate leaks in air ducts, let alone fix them. It is best to seek professional help with air ducts.

Inadequate fuel

It is also possible that your furnace is giving cold air because the gas supply was shut off. Ensure your furnace has access to a consistent gas supply. Get your furnace examined by a professional heating engineer to ensure your gas pipe is in good working condition.

fixing furnace giving cold air

How To Fix A Furnace Blowing Cold Air?

You must be thinking about what you should do if you have a furnace that is blowing cold air at your end. Don’t worry, we got you. Here are a few steps you can take once you are sure your furnace is blowing cold air.

Step 1: Ensure the thermostat is set to the right mode

Before jumping to the conclusion that your furnace is blowing cold air, ensure the thermostat is set at the desired mode. The thermostat should be set at heating mode and the fan should be set at “auto” mode. To know why the fan should be set at “auto”, refer to above.

Step 2: Check all your vents

The next step, check all your vents to ensure they are not blocked. Only an open vent will allow warm air to enter the house. Blocked or closed vents will stop your furnace from keeping you warm.

Step 3: Check the air filter

Further, check the air filter, a clogged filter would slow down the flow of air from a furnace. You should clean the dirt and debris accumulated in filters. Inspect furnace filters regularly and replace them when needed. Turn off the furnace system before accessing the air filter.

Step 4: Ensure consistent fuel supply

Check whether your furnace has access to adequate gas/fuel supply. In case of a gas leak, turn off the gas valve, switch off your heating system, exit the premises, and report the issue immediately. Don’t use any lighter or matches when working with a furnace.

Step 5: Contact professional HVAC services

We advise seeking professional help instead of DIYing your way around furnaces. Don’t be penny wise and pound (here dollar) foolish. Smile HVAC offers the best furnace repair services across many cities in Canada. To avail of the best services at pocket-friendly rates, contact us.

How to tell if your furnace is Malfunctioning and blowing cold air instead of warm?

Before we get into the whys and hows of a furnace giving cold air, how about a quick overview of the functioning of a furnace?

A motor fan in a furnace blows air across heating coils to produce warm air. Through ducts, this warm air enters your home to achieve the desired level of temperature indoors.

Look for the following signs as they indicate your furnace is blowing cold air instead of warm.

Furnace blowing nonstop

You likely have a case of a furnace blowing cold air if you feel cold even when the furnace fan is blowing. In other words, a lack of coordination between a furnace and its fan can cause cold air.

Cold spots around the house

If you feel uneven heating around the house, it could be a sign your furnace is blowing cold air. With a well-dispersed heating system, you can enjoy consistent temperature around the house. You deserve to experience a warm, cozy environment indoors with a high-quality furnace.

A furnace is not producing heat

When you use a furnace after months or weeks, it blows cold air initially. It is nothing to worry about. But, if a furnace blows low or has no heat on regular use, it could be a sign that something is wrong with your furnace. It could be a problem with the fan, belt, heating coils, or thermostat settings. Put your hand in front of air ducts, if you feel no heat/air, it means your furnace is giving cold air or no air at all.

Preventive steps to avoid a furnace from blowing cold air in future

No one likes expensive furnace repair bills. But, the question is how to avoid hefty repairs. Regular maintenance is the key to keeping your furnace in up and working condition. To prevent a furnace from blowing cold air in the future, book regular maintenance appointments. With regular inspections, professionals can identify and solve problems before they become worse. During a maintenance visit, technicians check the thermostat, filters, air ducts, and every part of the furnaces in detail. After a season of excessive use, get your furnace inspected. We recommend at least two maintenance services in a year. You all must have heard precaution is better than cure, similarly, in this case, prevention is better than hefty repairs.