Why Is My Furnace Not Blowing Hot Air?

While summer brings warm sunshine and ice-cold drinks, winter brings the holiday season and time to cozy up with loved ones at home. However, you’re less likely to enjoy the winter season if your furnace refuses to blow warm air.

If you and your family are shivering in your home, wondering, “Why is the furnace not blowing hot air?” fret not. Our team at A Custom Services knows how to restore your home’s heat through reliable furnace repair services in Chicago.

Before fixing the furnace, it’s important to know why it is malfunctioning. Below are common furnace problems and how to fix them.


Although your first thought may be to check the heating unit when the furnace fails to deliver warm air, you should check the thermostat first. The thermostat is integral to your home’s entire heating and cooling system. When it doesn’t work properly, it impacts furnace performance. 

For example, a broken thermostat fails to communicate properly with the furnace, which means your furnace doesn’t know how warm your home should be. As a result, it won’t blow sufficient warm air.

To see if your thermostat is the culprit, check the following:

  • The thermostat’s settings: It can be easy to bump into a thermostat and accidentally set it to “cool.”
  • The thermostat’s batteries: Dead or low batteries impact thermostat performance. 
  • The fan setting: If the fan is set to “on” instead of “auto,” it will blow cool air when it finishes the heating cycle.

If you determine that the thermostat is not the culprit, it’s time to check other parts of your home’s heating system. 


If you have a furnace not blowing hot air and the thermostat isn’t the problem, check the air filter. A dirty or clogged air filter can cause several problems for your furnace. Fortunately, it is also an easy fix. 

A clogged air filter restricts the system’s airflow, which means the furnace will struggle to warm and distribute air. In addition, some furnace systems automatically shut off when they detect dirty air filters to prevent dangerous overheating. 

Before calling an HVAC technician, check your furnace’s air filter. If it’s dirty, replace it as soon as possible. You can find air filters relatively cheap at local hardware stores.


The pilot light is responsible for warming the air in your furnace. As such, a failing pilot light can result in a lack of warm air and a frigid home.

Pilot lights are more common in gas furnaces; they ignite the burners to produce warm air. Although they usually burn continuously, a burst of air or various other things can easily put them out. 

To fix the pilot light, turn off your furnace for at least five minutes. Then, turn it back on and use a long-neck lighter to turn on the pilot light. If this doesn’t work, your system could have a failing flame sensor or another issue that requires professional attention.


As we said, the pilot light in your furnace ignites the burner, which heats the air the system blows into your home. If the burner is dirty, it can’t generate sufficient heat, leaving your system blowing cool air. 

Similarly, a broken or cracked heat exchanger means the furnace can’t heat your home’s air. Fixing the burner or heat exchange typically requires professional knowledge and tools. 


You can’t predict when your furnace will stop working, but you can take steps to avoid it. Regular maintenance is crucial for ensuring your system operates at maximum efficiency while avoiding expensive repairs down the line. 

One of the best ways to maintain your system is by replacing the furnace filters regularly. Dirty or clogged air filters can negatively impact your furnace’s efficiency, prevent it from delivering warm air, and cause it to overheat. Replacing filters at the end of every season helps ensure your system continues running efficiently while keeping your home’s indoor air clean.


Is your furnace not blowing hot air, and you’ve gone through all the troubleshooting steps? Let our technicians at A Custom Services help. We know how to identify the problem and provide a prompt, effective solution.

Whether you need a fast repair or help creating your furnace maintenance checklist, we have you covered. Call our team at A Custom Services at (773) 207-7551 today!

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