Why is my Furnace Blowing Cold Air?

If your furnace is blowing cold air during a Calgary winter, it is often caused by a few common and manageable issues. We recommend performing these checks to restore warmth to your home:

• Check your thermostat settings: Ensure the thermostat is set to “Heat” and the fan is set to “Auto.” If the fan is set to “On,” it will blow air continuously even when the furnace is not heating. Also, confirm the target temperature is higher than the current room reading.
• Inspect the air filter: A clogged or dirty filter restricts airflow, which can cause the furnace to overheat and trip the limit switch. This safety feature shuts off the burners while the fan continues to run, resulting in cold air. Replace the filter if light cannot pass through it.
• Examine the flame sensor: A dirty flame sensor can cause the furnace to shut down or short cycle. You can clean the sensor—a metal rod near the burner assembly—using a dollar bill or fine-grit sandpaper to remove buildup.
• Interpret furnace error codes: Look at the LED diagnostic panel near the blower compartment. Flashing lights often indicate specific issues, such as a limit switch or flame sensor fault. You can try to clear the code by shutting off power at the breaker for 30 seconds, but if the code returns, professional service is needed.

If these steps do not resolve the issue, or if you hear unusual banging or squealing noises, it may indicate a mechanical failure. In Calgary’s sub-zero temperatures, a failed furnace is a safety priority. With over 25 years of experience, we provide 24/7 emergency response to ensure you are Providing Comfort every hour, in every season.

• Furnace Troubleshooting Guide: Quick Fixes for Homeowners