Why is My Furnace Blowing Cold Air

Angry woman suffering cold complaining in a bed in winter.

Your furnace is running, but the air blowing out of the vents sends a shiver down your spine. It’s a frustrating situation, and one that might not make a whole lot of sense.

This is actually quite common, but in order to find out why your furnace is blowing cold air, some troubleshooting is required. A number of components could be the culprit!

  • Your air filter is dirty or blocking air flow. If your air filter is letting air pass freely, then the furnace will quickly overheat itself. As a result, a safety mechanism will shut down the whole furnace and run the fan to cool itself off. This mechanism is called the limit switch. One telltale sign of a dirty air filter is if your furnace alternates between hot air and cold air, or stops blowing on its own accord. If this is the case, change the air filter ASAP! With a dirty air filter, you’ll be losing money on a bigger energy bill while also putting yourself at risk of a home fire — not to mention the chilly temperatures.
  • Your thermostat is set to ON rather than AUTO. It can be a little confusing — what’s the difference between ON and AUTO, anyway? ON means your fan will always be on, regardless of whether or not the furnace is actually heating. When the furnace isn’t running, the fan will simply circulate room temperature air — it only feels cold because it’s moving. This is can be done economically if you have a high efficiency DC fan motor. AUTO, on the other hand, means the fan only runs when the furnace is heating. We recommend leaving your thermostat on AUTO – as it’s much more energy efficient for those with standard fan motors.
  • Your pilot light is out. Another common culprit is the pilot light. This is especially frequent with older furnaces. Every once in awhile, the pilot light might blow out and require relighting. If your furnace is still blowing cold air, it might be an igniter malfunction, gas supply problems, or a clogged condensate line. With these issues, it’s best to call a professional.
  • Your thermostat isn’t set to HEAT. No judgement here…everyone makes simple mistakes every now and then! Make sure your thermostat is set to HEAT along with AUTO before moving forward.

Still having trouble locating the problem? Call Great Dane HVAC to talk to a friendly, experienced HVAC technician to track down the problem and get to work on a solution. Don’t wait out the cold any longer — call today!

Need HVAC Service?

Contact the experts at Great Dane Heating & Air Conditioning.

Call us at 586.790.2604!