Why is My Furnace Blowing Cold Air?

There’s nothing quite like the bone-aching struggle to clear the snow off your sidewalk while facing a 30 mph cross-wind blowing directly into your eye. After the task is done and you limp through your home in your frozen pants like a combination robot/scarecrow, the warmth of the furnace encompassing your whole body is starting to become a reality. You hear the rumble in the blower motor and the hot air working its way through the ducts only to deliver an arctic blast of cold air into your face….

“Furnace, you had one job.”

When your furnace is blowing cold air it’s really no longer a furnace is it? This is not only a nuisance but a legitimate danger that could compromise the sanctity of your home’s pipes, electronic components, and other features such as your body, that should be kept above freezing temperatures. The winter is hard enough, you don’t need a furnace blowing cold air to pile on to the misery so here’s what could be causing these issues:

Furnace blowing cold air

Knowing the Four Main Areas of the Furnace  

When a furnace stops running as it’s supposed to for any reason, the cause is found in one of the four main areas of the unit:

Fuel

Air is heated in a furnace by fuel so if there are compromises within this component the air will still blow, but it won’t be warmed. Electricity could also be considered part of the fuel source since it ‘fuels’ the components needed to run that type of system. Some possible issues within the fuel source include an empty oil tank, gas supply valves shut, electric furnaces turned off, or breakers flipped. Also, if the fuel doesn’t adequately get to the furnace (clogged filters, leaks, corroded wires) it could cause cold air to blow.

Burners

The burner is needed to provide the flame to light the fuel and warm the air. Obviously when air is delivered but not heated, there could be problems with the burner. The easiest fix is a pilot light that has gone out and just needs to be lit back up. The flame sensor could also need cleaning with a steel wool pad which is another easy fix as is the cleaning of a condensate drain which can prevent the burner from lighting. If there are problems with the control valve it’s best to have a service tech take a look.

Fan

Usually if a furnace is blowing air, but it is cold, there generally isn’t a problem with the fan itself. That being said associated components definitely can affect the performance of the fan, specifically a clogged air filter. When the fan has to push air through layers of dirt and debris it will be less effective and clogs can also shut down the burner as well which could be why the air is blowing cold. Filters should absolutely be replaced as frequently as every 30 days, if anything, to help reduce efficiency bills.

Ducts

Sometimes there is nothing wrong with the heat creation part of the furnace and instead the issue of cold air blowing is caused instead by the heat delivery. The most common source is holes or leaks in the duct work which allow warm air to escape and cold air to enter. Other issues such as a closed damper could also be causing most of the warm air to be sealed from reaching the intended rooms.

It’s likely that one of these areas is the cause of your cold air coming from the furnace problem. If DIY fixes do not solve the problems make sure to call a qualified service tech – we won’t shovel your sidewalks, but we’ll deliver warm soothing relief after you’re done doing so.

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