Help! My Furnace is Blowing Cold Air

If your furnace is blowing cold air, the good news is your blower is working. This fact provides little comfort as the temperature drops outdoors in St. Peters, MO. Here are some potential reasons your furnace could be malfunctioning and solutions to help solve your problem.

#1 Did you just switch your furnace on?

If your furnace has been dormant since last heating season, be patient. Like preheating your oven, it takes a few moments for warmer air to stream from your vents. Remember the parking in tandem rule. Existing cold air must exit the vents first, followed by warm air.

You turned on a furnace in the basement that needs to activate, blow air over the heat exchanger to warm it, and send the warm air to your ductwork to displace the existing cold air. The air flowing from your vents should change from cold to warm momentarily.

#2 Have you checked your thermostat?

Your thermostat provides two clues to a case of cold air. First, ensure your system is neither off nor in cooling mode, it should be on heating mode. Second, the fan may be ON rather than AUTO mode. ON is not a problem, but realize the air continues to circulate whether it’s being conditioned or not.

#3 When was the last time you had your furnace serviced or replaced the air filter?

An annual furnace check is always recommended. Besides restoring your St. Peters furnace to peak efficiency, damage is addressed early and all parts are cleaned.

One of the common reasons for cold blowing air from a furnace is a dirty sensor. The sensor detects the burner. If a lit burner goes undetected, the gas supply to your furnace is shut off as a safety precaution. No gas equals cold air from your furnace. In the same way, an extinguished pilot light on older furnaces shuts off the gas.

If you haven’t replaced your furnace air filter regularly, it may be dirty. A clogged air filter can damage the heating components of your furnace. The damage can accumulate and cause furnace failure.

Whether the solution to cold air from your furnace is simple or complex, a Hoffmann Brothers qualified HVAC contractor can help. Call (314) 664-30111 in St. Peters, MO. for a reliable fix when your furnace is blowing cold air.

For more information on all your furnace needs, visit our website at:

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