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Why Your Furnace is Blowing Cold Air

A furnace blowing cold air is not only a nuisance, but a danger to your home's pipes, electronic components, and home comfort. Here are the four main reasons why: Fuel The air in your furnace is heated by fuel. If there are compromises within the component, air will still blow, it just won't be hot. (Electricity is also considered part of the fuel source since it runs the entire system.) Possible issues within the fuel sources that will cause cold air to blow:

  • Empty oil tank

  • Gas supply valve shut

  • Electric furnace turned off

  • Breakers flipped

  • Fuel source cut off due to clogged filters, leaks, or corroded wires Burners A furnace's burner is needed to provide the flame to light the fuel that warms the air. So, when air isn't delivered, it isn't heated. Possible burner issues:

  • Pilot light has gone out and needs to be lit again

  • Flame sensor needs cleaned

  • Condensate drain needs cleaned

  • Control valve problems - hire a professional for this one. Fan Cold air is not caused by the fan itself. It's usually due to a clogged air filter where the fan has to push through layers of debris, making the fan itself less effective (change your filters every 30-90 days). Ducts At times, there is nothing wrong with the heat creation but instead the delivery. The most common sources are:

  • Holes or leaks in the duct work

  • Closed damper Is your furnace blowing cold air? Call 72 Degrees Comfort Company at 515-965-7272 or email us at

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