Snell Heating & Air Conditioning

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Why Is My Furnace Blowing Cool Air?


What’s worse than a furnace blowing cool air on a frigid winter day? You may be thinking “not much” and we would have to agree with you. Cool air coming from your furnace can be caused by a variety of reasons – see below for some of the possibilities:

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A furnace consists of four major components, each of which must be working correctly for it to supply heat to your home. The components consist of the fuel system, the burners, the fan, and the ductwork.

Heat SourcesWhy Is My Furnace Blowing Cool Air?

Fuel is the heat source of any furnace. For systems that use gas, the gas supply valves must be open to allow the fuel to get to the burners. In an electric system, the breaker must be set to the “on” position at the main panel.


  • Filters: changing or cleaning your filter is of the utmost importance when maintaining or troubleshooting your furnace. A clogged or dirty filter can block airflow and limit the heating capability of your fan as it blows through a clogged filter. In some cases, a clogged filter can even shut down the burner and cool air will blow through the system as a result.
  • Condensate Lines: cool air blowing from your furnace can also be a result of a clogged condensate line. A clog can prevent the reservoir float from opening which will prevent the burners from lighting and producing heat.
  • Ductwork: broken or damaged ductwork including holes will cause cool air to flow into your home. Even if your furnace is blowing warm air, it can feel cool by the time it blows out of your vents if your ductwork is not properly sealed.

Troubleshooting a furnace can be a difficult task and should be left to professionals. If you experience a problem, give the heating and cooling experts at Snell a call and we’ll be glad to come by to diagnose the problem. Don’t forget to connect with us on Twitter!