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Ask John Furnace Blowing Cold Main Image

Why Is My Furnace Blowing Cold Air?

John Turpin is our resident home service repair expert here at Service Direct. He’s got the knowledge and experience to help homeowners like you make sense of most home repair issues. And with Service Direct, we connect you with top-tier service professionals to help with any repairs needed.

Find the Reasons Why Your Furnace Keeps Blowing Cold Air

Blowing cold air could mean something’s wrong with your furnace. It could be an issue with the thermostat, flame sensor, air filter, gas supply, or motor. The furnace blowing cold air might also be the result of overheating.

As you know, furnaces help heat homes. If it’s producing cold air instead, it needs prompt inspection. You can call a local HVAC professional for a furnace inspection, but you may be reluctant due to scheduling, fees, and other outside factors.

Now, you’re wondering, can you fix your furnace on your own? Fortunately, furnaces are not too complicated and you can resolve it the issue of it blowing cold air if you have basic knowledge and understanding of how it works.

With that said, we’re here to help you out by providing some answers to the question, “Why is my furnace blowing cold air?” Read on to find out the most common reasons why your furnace isn’t blowing warm air and how to troubleshoot it.

Reasons Furnace Blows Cold Air
Check out the list below for the most common causes your furnace is blowing cold air.

Common Reasons Your Furnace Is Blowing Cold Air

A reliable and efficient furnace is crucial for keeping your home warm during the cold winter months. That’s why it’s understandably frustrating when your furnace starts blowing cold air. But don’t worry because we’re here to help you learn potential solutions to address this problem. Check them out below!

Thermostat Settings

One of the first things to check when your furnace is blowing cold air is the thermostat settings. Ensure that it’s set to “heat” mode and that the temperature is set to higher than the current room temperature. It’s also helpful to check if the thermostat is functioning correctly. If it’s not set correctly, and the furnace continues to blow cold air, go check other possible causes.

Malfunctioning Thermostat

A furnace blowing cold air when shut off could also be because the thermostat is malfunctioning and not properly communicating with the furnace. Check if the thermostat’s batteries need replacement and ensure the settings are accurate. If it is indeed faulty, consider replacing it or contacting a professional for further troubleshooting.

Airflow Obstructions

Restricted airflow can hinder your furnace’s ability to generate and distribute warm air effectively. Check for any obstructions, such as closed or blocked vents, dirty air filters, or debris around the furnace. Dirty or clogged air filters restrict airflow, making the furnace work harder and may potentially lead to cold air blowing from the vents.

Clean or replace the air filters, and ensure that vents are open and unobstructed. Improving airflow can often resolve the issue of a furnace blowing cold air.

Pilot Light or Ignition Problems

For furnaces equipped with a pilot light, a malfunctioning or extinguished pilot light could be the cause of cold air blowing from the furnace. Resolve it by following the manufacturer’s instructions to relight the pilot light.

If it continues to go out, or if your furnace has an electronic ignition system, you should contact a professional HVAC technician. They can diagnose and repair the issue, as they have the necessary expertise to identify the problem and take appropriate measures.

Faulty Flame Sensor

One of the possible answers to your question, “Why is my furnace blowing cold air sometimes?” is a faulty flame sensor. A malfunctioning flame sensor can cause the furnace to shut off the gas valve, preventing the burners from igniting.

This safety mechanism ensures that gas is not released into your home if the burners don’t ignite properly. A dirty or corroded flame sensor may not detect the flame and can result in cold air blowing from the furnace.

Cleaning or replacing the flame sensor can often resolve this issue. Refer to your furnace‘s user manual for instructions on cleaning. Or, you can contact a professional technician to help repair or replace the sensor.

Our resident home repair guru, John Turpin, discusses some of the most common reasons why your furnace is blowing cold air as well as some DIY remedies.

Gas Supply Issues

If your furnace runs on natural gas or propane, a disruption in the gas supply can lead to the furnace blowing cold air. Check other gas appliances in your home, such as a water heater or a gas stove, to see if they are functioning correctly.

If they’re not, it indicates a potential gas supply issue. In such cases, contact your gas supplier to investigate and resolve the problem as soon as possible. It’s crucial to prioritize safety when dealing with gas-related problems and consult a professional if needed.

Malfunctioning Blower Motor or Control Board

The blower motor in your furnace is responsible for circulating warm air throughout your home. On the other hand, the control board regulates various functions of the furnace. If any of the two malfunctions, it can lead to cold air blowing out of vents when the heat is on.

If you suspect any issue with either component, it’s recommended to seek assistance from a qualified HVAC technician. With their expertise, they can effectively diagnose and repair problems related to the blower motor or control board.

Improper Sizing of Furnace

If your furnace is too small for your home, it may struggle to generate enough heat to maintain a comfortable temperature. Inadequate heating capacity can lead to the furnace running continuously but only blowing lukewarm or cold air.

In such cases, consulting with an HVAC professional to assess the sizing of your furnace should help. An HVAC professional can recommend an appropriate size for your home that can resolve the cold air problem.

Ductwork Issues

Issues with your ductwork can also contribute to the furnace blowing cold air only at night, or even all the time. Leaks, gaps, or disconnected ducts can allow warm air to escape before it reaches the desired areas. Inspect the ductwork for any visible issues and, if necessary, contact a professional to assess and repair the ductwork.

Encountering a furnace blowing cold air can be a frustrating experience, especially during the winter season. By troubleshooting common causes, such as thermostat settings, gas supply issues, and ductwork problems, you can identify the root cause and take measures to resolve it.

Furnace Ductwork Issues
Whether there’s an issues with the thermostat, gas supply or ducting a HVAC technician can help.

Furnace Blowing Cold Air FAQs

Can I troubleshoot the issue myself?

Yes, you can. There are certain troubleshooting steps you can take before contacting a professional. These include checking thermostat settings, relighting the pilot light (if applicable), ensuring proper airflow, checking the gas supply, cleaning or replacing the flame sensor, and inspecting and cleaning air filters. But for complex issues or if you’re unsure about any aspect, it’s best to seek professional assistance.

Can a furnace blowing cold air be fixed, or do I need to replace it?

In many cases, a furnace blowing cold air can be repaired by addressing the specific cause of the issue. But there may be instances where the furnace is old, inefficient, or has major components that are beyond repair. In such cases, replacing the furnace might be the most cost-effective and practical solution.

How often should I have my furnace serviced?

Generally, it is recommended to have your furnace serviced at least once a year. Ideally, it should be done before the start of the heating season. Regular professional maintenance helps ensure optimal performance, efficiency, and early detection of any potential issues. Consult the manufacturer’s guidelines or follow any specific recommendations provided by your HVAC technician.

Are there any energy-saving tips related to my furnace?

Yes, there are some energy-saving tips you can try with your furnace. These include programming your thermostat to lower temperatures when you’re away or asleep, sealing air leaks around doors and windows, using ceiling fans to circulate warm air, and improving insulation in your home. Also, consider upgrading to a more energy-efficient model if your current model is old and inefficient.

Hire a Local HVAC Pro

Some issues can be addressed by homeowners, but it’s important to recognize your limits and contact a professional HVAC technician for complex repairs or gas-related concerns. More importantly, regular maintenance and prompt repair help ensure the efficiency of your furnace.

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