My Furnace is Blowing Cold Air – What’s Wrong?

Published on: October 23, 2013

When it gets cold enough outside that you need to turn on your heating system, the last thing you expect is to find that your furnace is blowing cold air.

The cool air is not necessarily a sign that you need to replace your furnace. The reason your furnace is not blowing hot air could be something very simple or a reason to call for service.

It is perfectly normal for your furnace to blow cool air when you initially turn it on. The cool air is merely the air that is trapped in your vents. After a few moments, the air should be warm. If your furnace is blowing cold air after being on for five minutes, something may be wrong.

A common reason for a furnace to blow cold air instead of warm is that the thermostat is not on the automatic setting. When your programmable thermostat is set to “on” instead of “auto,” the fan runs all the time, blowing cold air when the furnace is not running. The automatic setting only turns on the fan when the furnace is actually running. Adjusting your setting may solve your problem.

If you have an older gas furnace, check your pilot light. The pilot light is the flame that ignites the gas to create heat. If the light goes out, your furnace will only blow cold air. Relight your pilot according to the instructions on your furnace. A pilot light that won’t stay lit is a sign that you need maintenance.

While some furnace problems can be easily fixed by a homeowner, there are other issues, such as a dirty flame sensor or a faulty igniter, that require professional service. If your furnace is blowing cold air and you cannot resolve the problem with the tips above, use AC Southeast® to find a contractor in your area of the southeastern U.S.