When the cold weather arrives, and you have to turn on your furnace for the first time after many months of not using it, the last thing you want to discover is that it isn’t working. Even worse, you feel your furnace blowing cold air. It can be very annoying to have to deal with a broken furnace at the point when you need it the most.

There’s no need to panic. As frustrating as this problem is, the answer could be an easy fix. Here are a few reasons for your furnace blowing cold air.

With most of these, you can correct the issue yourself. For some, though, you’ll have to call for assistance from an HVAC repair professional.

Furnace Not Blowing Warm Air

If you get a burst of cold air when you first turn on the furnace, but after a few minutes the air is warm, that is nothing to be worried about. It’s typical for cold air to come out of the vents at first since the furnace has to warm up. It’s like turning on the hot water. You get cold water first. The same thing happens with your furnace. It has to push out the cold air before the warm air can come. Of course, if warm air doesn’t come out after a couple of minutes, something may be wrong, and it’s time to call a heating and cooling company.

The Thermostat is at “On”

If there’s a continuous flow of cold air coming out of your furnace, look at your thermostat to see if the system’s fan is set to “auto” or “on.” Probably, the fan setting on your thermostat is at “on,” meaning your furnace blower will continually operate even when your furnace isn’t blowing out warm air. By changing the thermostat to “auto,” the fan operates only when the furnace is blowing warm air.

Dirty Flame Sensor

Ignition furnaces that are pilotless use a flame sensor to operate the furnace. If you have a dirty flame sensor, your furnace will turn on and start heating then become cold very fast.

If you know about furnace parts, you can clean the flame sensor, which should re-establish your furnace’s heating task. You could also use the services of an HVAC repair specialist to clean the sensor for you.​