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Why Is My Furnace Blowing Cold Air?

If you live in a country that experiences extreme weather conditions like freezing winter seasons, you probably have a furnace responsible for warming up your house. No homeowner wants to arrive home from the office or work just to find out that their furnace is not heating the house. Why is my furnace blowing cold air? Many individuals end up confused and wondering why their furnace won’t warm the house up even after switching it on. 

Fortunately, one might be able to troubleshoot their furnace and even solve the problem if the system is undergoing a basic and simple breakdown. Therefore, you should consider various factors first to check up on your furnace before calling HVAC technicians for assistance.

Reasons Why Your Furnace Is Blowing Cold Air

If you notice that your furnace might be blowing cold air into your rooms regardless of turning it on, you should troubleshoot certain components in the system to know what the issue might be. Hereby, we are going to take you through a few reasons that might alter your furnace’s heating system. Let’s delve into it:


  1. Improper thermostat configuration

If your home is occupied by several family members, you might probably be experiencing ‘thermostat wars’ in the house. This means that some individuals might change the thermostat setting in their favor. Someone might have switched the thermostat from AUTO to ON last night to cool down the room may be due to rising night temperatures. 

Leaving the thermostat setting ‘ON’ will keep the furnace blower ON, and blowing even when your furnace is not heating air. Turn the setting back to AUTO to bring your furnace’s performance back to normal. 

  1. An overheated furnace

The overall heating in your furnace mainly happens in the heat exchanger. If your heat exchanger happens to overheat at any point, the system will automatically detect the situation and switch the burners off immediately. 

It will however leave your blowers running thus causing your furnace to keep blowing cold air in the room. The blowers will help cool your furnace down. An overheating furnace might be a result of a damaged or clogged air filter. 

  1. Inadequate gas supply

If your furnace is on and your thermostat setting is correct and your system is still not heating the house, then it must be something to do with your gas supply. For your furnace to work properly and efficiently, it requires an adequate gas supply to produce heat in the system so that the burners remain efficient. 

If your furnace receives inadequate gas supply or no gas at all, its pilot light will not light up and you’ll have to stay in the freezing cold through the night. This might be caused by a disconnected line or if your gas supply is cut from the source. 

You might be sitting shivering at home still asking yourself, ‘why is my furnace blowing cold air?’ This might be the main cause of your furnace problem. Contact the HVAC professionals as soon as possible to help you solve such an issue. 

  1. A clogged filter

A clogged or blocked air filter will always be a problem for your furnace or air conditioning system. If dirt, dust, and debris accumulate in your filter, it will end up blocking thus restricting the amount of airflow coming into your furnace. 

Restricted airflow to your furnace results in overheating thus leading to breakdowns. If your filter is clogged you might have to either clean it or replace it with a new one. 

  1. If the pilot light is off

Traditional furnaces are known to have pilot lights that are set to stay on and keep the gas ignited for your furnace’s burner. If your pilot light happens to go out, then the furnace won’t heat your room anymore. 

You’re advised to read through your manufacturer’s manual to relight the pilot light safely and get your furnace back to work. You’re however recommended to call an expert if the issue seems complex, to make sure you don’t cause any accidents. If you’re handling your pilot light for the first time, you’d rather call a technician for help than handle this yourself. 

  1. A dirty flame sensor

Furnaces that don’t have a pilot light ignitor have a flame sensor that makes sure your furnace keeps burning after ignition. If your furnace’s flame sensor is clogged, your heating system might go off a few minutes after it’s switched on. 

This will make your furnace start blowing cold air. One can clean their flame sensor by themselves or contact a professional if the task seems challenging to you. 

  1. Thermostat problems

If you’ve owned a furnace for quite some time now, you’ll realize that the thermostat is the key cause of random breakdowns across your furnace. 

If you don’t understand how your thermostat works, you might be amongst the furnace users frequently asking ‘why is my furnace blowing cold air?’ If you notice that your furnace has stopped heating the house, you’ll obviously rush to troubleshoot your thermostat first. 

If your thermostat is not adaptable to your furnace, your heating system might fail to heat your home properly. You’re recommended to consult your manufacturers or HVAC technicians about a new thermostat for replacement. 

Why Is My Furnace Blowing Cold Air – Conclusion

If your furnace is not heating up even after switching it on, you’ll have to check up your whole system to know what the cause of the issue might be. 

Many homeowners usually freak out when this happens and they’re always on the internet searching, ‘Why is my furnace blowing cold air?’. Relax and take your time to troubleshoot your furnace since it might probably be a simple breakdown that you can solve on your own. 

You don’t have to worry about the repair costs since this is possibly a cheaper one. We recommend you contact and keep in touch with your HVAC technicians for regular maintenance and repair schedules which will help keep your furnace going. 

Use this article to troubleshoot your furnace whenever you notice that it’s been blowing cold air instead of warm air to your rooms.

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