Common Causes of Furnace Blowing Cold Air

During winter, furnaces are crucial to keeping your home warm and comfortable. But what if you walk into your cold home to find the furnace blowing cold air? What’s causing this problem? Several things can cause the issue, and here are some of them.

1. Incorrect Thermostat Setting

It is possible that your thermostat setting may be incorrect if your furnace is blowing cold air. However, before calling a professional, you can verify this by checking the temperature setting on the thermostat.

Ensure it is set to at least 65 degrees Fahrenheit while you’re sleeping or away from home. If the furnace continues blowing out cold air after changing the thermostat setting, you may want to contact a professional.

2. Thermostat is Malfunctioning or Broken

An important part of your furnace is the thermostat, and if it isn’t working, it will be unable to deliver warm air to your home. Instead, you can check the thermostat by placing a thermometer in the room where you are located. Once you have done this, adjust the temperature settings on the thermostat to match where the thermometer is placed.

If you see that there isn’t a temperature change, then there may be a problem with your thermostat, and it may need replacing.

3. Blown Heater

The heater can be the main culprit if your home is cold and the furnace is blowing cold air. If the furnace has a blower motor, you should try turning it off and then on again. That will completely restart the process, which will help clear any debris or problems with your blower motor. If you turn off the thermostat while trying this, you may also want to try using a different thermostat.

4. Empty Oil Tank

If your furnace is partially empty of oil, it may be unable to create warm air. The cause of this problem can vary between models, but an empty tank often means that the furnace cannot create the heat necessary to keep your home warm and comfortable. If you find there is oil in the furnace, and it continues to be cold, you may want to contact a professional.

5. Clogged or Dirty Air Filters

A clogged air filter is another issue that can be the cause of the furnace blowing cold air. This problem can affect your furnace’s performance, affecting your ability to stay warm. You should check the air filters weekly, but if you see that they are dirty or clogged, you may want to change them immediately. After changing the filters, turning your blower off again is a good idea, as this helps your furnace reset itself.

6. Damaged Pilot Light

If your furnace is working fine but blowing cold air, it may be due to a broken pilot light. You will be able to see a flame when you first turn on the pilot light, and this indicates that the heating system is ready for use. If there is no flame when you turn on the furnace, then the problem lies with your pilot light, and you will need to call an expert for repairs.

7. Damaged Duct Work

Damaged ductwork could be te reason your furnace blows cold air. Ducts are crucial to your furnace’s ability to provide warm air throughout your home. If the ducts are damaged or not properly connected, the ventilation system will not be able to create warm air, and you may see that the furnace keeps blowing cold air. Call a professional if you believe that this is what is causing your furnace to blow cold air.

8. Faulty Thermocouple

The thermocouple is an internal part of the furnace responsible for shutting off the furnace if there are any problems. The thermocouple may be inside if you have a boiler, but it still performs the same function. The furnace can continue to heat up if the thermocouple is faulty. Make sure that you check and replace your thermocouple if this is what is causing your furnace not to work properly.


The furnace is crucial to keeping your home warm and can go out of commission if you do not take care of it. Knowing the common causes, you can avoid these problems and keep your furnace running properly. If this is something that you have experienced and need assistance with, then contact a professional as soon as possible.

Author – Sylvia