On a cold night in Irmo, SC, you’ll turn to the thermostat to start up your furnace. If your furnace blows cold air through the vents, this is a most unwelcome surprise. A range of issues could cause this, and some of them can be taken care of without a service call. Read on to learn three reasons why your furnace is blowing cold air and what to do about them.

Dirty Air Filter

A dirty air filter is the most common reason why furnaces blow cold air. When the filter is clogged, the heated air can’t pass through it. The warmed air stays in the combustion chamber, where it may cause the furnace’s heat exchanger to overheat. When the warmed air is stuck in the combustion chamber, the heating system can only blow the room-temperature air that’s already in the vents. According to Energy Star, you should check the furnace filter once per month. Replace it when it’s visibly dirty, and don’t wait longer than three months between filter changes.

Improper Thermostat Setting

Check your thermostat’s fan setting. If it’s set to “on,” this could be why cold air sometimes blows from your home’s vents. This setting causes the fan to be on all the time, even when the furnace isn’t performing a heating cycle. A fan that’s constantly on will blow cool, room-temperature air during these intermittent periods of time.

Pilot or Igniter Problem

If you have an older furnace blowing cold air, its pilot light may have gone out. You can check the heating chamber to see if there’s a flame or not. The owner’s manual should explain how to relight the pilot. If you have a newer furnace, it may have an igniter problem preventing the burners from lighting. This requires a professional heating repair.

For more information about why your furnace is blowing cold air, take a look at Cassell Brothers Heating & Cooling’s furnace repair services, or call us today.