Why is My Heater Blowing Cold Air?

Heater Blowing Cold Air

Just when you thought it was going to stay mild, the temperature has dipped and now it’s below zero. You flip the switch for the furnace only to find that it’s blowing cold air. Now, it feels colder inside than it does outside. There are many reasons why your furnace is blowing cold air. Read on to learn why this happens and when to call an HVAC professional.

Check the Thermostat

One of the most common reasons a furnace blows cold air the thermostat setting. Make sure that your thermostat is set on auto in your HVAC unit. In this way, it will automatically switch to the furnace function when the temperature drops below a certain level.

Check the Air Filter

Dirty air filters can also cause your furnace to blow cold air. When air filters are clogged, it can block the air exchanger in the furnace, which not only causes it to blow hot air, but may also cause your furnace to overheat. Make sure the air filter is always clean and free of dirt and debris. If you have pets, you might need to check and change your air filter more often.

The Pilot Light is Out

If you have an older furnace, the pilot light might be out. To relight the pilot light, first switch the thermostat from heat to off. Locate the furnace's pilot light and accordingly the manufacturer's instructions, relight the pilot light. If in doubt on how to do so or if the furnace still blows cold air, consider enlisting the help of a HVAC professional to help get your furnace working properly.

Inspect the Ductwork

Ductwork that needs cleaning can also cause your furnace to blow cold air. Over time, dust, dander and debris can accumulate, which can block proper airflow. If you think this is the case, you should contact a qualified HVAC professional for inspection.

Broken Flame Sensor

If your furnace starts blowing hot air only to quickly turn cold, your flame sensor may be to blame. If the flame sensor is coated with residue, it's unable to gauge the temperature properly. It then lowers the temperature and blows cold air.

Now's the time to ensure your furnace is ready for winter. Whether your furnace is blowing cold air or you need seasonal HVAC maintenance, we're here for you. Contact Ardmore Fresh Air to schedule a service call.


Contact Ardmore Fresh Air at (847) 792-1019 for your next appointment or any questions regarding our blog articles! In a hurry? Schedule your appointment online now.