Why Is My Air Conditioner Blowing Warm Air?

Why Is My Air Conditioner Blowing Warm Air?

Air conditioning systems have become an indispensable part of our lives, especially during the scorching summer months. When functioning correctly, these systems deliver a constant flow of cool air that helps maintain a comfortable indoor environment. However, there may be times when your air conditioner starts blowing warm air, disrupting your comfort. This blog post aims to shed light on why this might occur and how to rectify it.

The Basics of How an Air Conditioning System Works

Before we delve into the potential reasons behind the issue, it’s crucial to understand how an air conditioning system works. At its core, an air conditioner works on the principles of heat transfer, fluid dynamics, and evaporation.

The system is composed of three main components: the compressor, the condenser, and the evaporator. The compressor, located in the outdoor unit, compresses the refrigerant gas, thereby raising its temperature and pressure. The hot, pressurized refrigerant then flows into the condenser, where it releases heat to the outdoor air and condenses into a high-pressure liquid.

This high-pressure liquid refrigerant then travels to the evaporator inside your home. As it flows through the evaporator coils, it evaporates into gas, absorbing heat from the indoor air in the process. The heat absorption process ultimately cools the air, which the blower motor then circulates back into your home. The refrigerant gas then returns to the compressor, and the cycle repeats.

Possible Causes of Your Air Conditioner Blowing Warm Air

When your air conditioning system is blowing warm air, there can be several root causes.  Your professional HVAC technician will work diligently to pinpoint the issue before repairing your AC.

Clogged Air Filter

The air filter in your HVAC system plays a pivotal role in maintaining the quality of your indoor air. It filters out dust, pollen, pet dander, and other pollutants, preventing them from circulating throughout your home. However, over time, these particles build up on the filter, causing it to become clogged.

A clogged air filter restricts the flow of air into your air conditioning system. This limited airflow can cause the system’s evaporator coil to freeze up due to inadequate heat exchange. When the system’s coil is frozen, the coil cannot absorb heat from the air. As a result, the air conditioner blows this warm air into your home.

We recommend that you check your air filter at least once a month and replace it as needed, generally every 60-90 days. However, homes with pets or people with allergies may need to replace the filter more frequently.

Thermostat Set Improperly

Your thermostat is the control center for your air conditioning system. A simple misconfiguration can lead to your air conditioner blowing warm air.

If your thermostat is accidentally set to “heat” instead of “cool,” it will direct your system to warm your home. Likewise, if the fan setting is switched to “on,” the fan runs continuously, even when the air isn’t being cooled, which can give the impression that your system is blowing warm air.

Always double-check your thermostat settings. Set your system to “cool” and the fan to “auto” for the most efficient operation.

Low Refrigerant

Refrigerant is the lifeblood of your air conditioning system. It’s the substance that absorbs heat from the indoor air and releases it outside, thereby cooling your home.

When the refrigerant level is low, your air conditioner can’t absorb enough heat to cool the air effectively. Low refrigerant levels usually indicate a leak leak in the refrigerant lines, a problem that requires professional attention. Prolonged operation with low refrigerant can lead to further damage, including compressor failure, making it critical to address this issue.

Outdoor Unit Lost Power

Your air conditioning system comprises two primary components: the indoor unit (containing the evaporator coil and blower) and the outdoor unit (housing the compressor and condenser). The system needs both to be powered in order to cool your home effectively.

If the outdoor unit loses power due to a tripped breaker, blown fuse, or wiring issue, but the indoor unit continues to run, the system will be unable to cool the air. As a result, the blower will circulate warm air throughout your home.

Faulty Expansion Valve

The expansion valve plays a critical role in the refrigeration cycle. It controls the amount of refrigerant entering the evaporator coil, ensuring it’s the right amount to absorb the heat from your indoor air.

If the expansion valve is faulty, it can cause too much or too little refrigerant to enter the evaporator. Both scenarios disrupt the cooling process. Too little refrigerant, and there won’t be enough to absorb the heat effectively. Too much, and the coil can become too cold and freeze over. In either case, your air conditioner may start blowing warm air.

Blocked Condensing Unit

The condensing unit, located outdoors, is responsible for releasing the heat absorbed from your home to the outside environment. For it to function effectively, it needs adequate airflow.

The condensing unit can’t expel heat as efficiently if it is blocked by debris, leaves, or other obstructions. The system may overheat and go into a safety shut-off mode to prevent damage, or it may continue to operate but with reduced efficiency. This inefficiency can lead to the system’s inability to cool the air properly, causing it to blow warm air into your home.

To prevent this, ensure the area around the condensing unit is clear of debris and there’s sufficient clearance for proper airflow. Regularly check the unit, especially during fall when leaves may accumulate, and after storms that could leave debris nearby.

By understanding these potential causes, you can take proactive steps to keep your air conditioner functioning optimally. However, some issues, such as a refrigerant leak, faulty expansion valve, or power issues with the outdoor unit, require professional attention. That’s where The Otter Guys can help, providing expert maintenance and repair services to keep your system running at its best. Their team of professionals can diagnose and address these problems, ensuring your home remains cool and comfortable.

The Importance of Air Conditioner Maintenance

Now that we’ve explored the potential reasons why your air conditioner might be blowing warm air, it’s crucial to discuss preventative measures. Regular maintenance of your air conditioning system is the best way to prevent such issues from arising.  The good news is that The Otter Guys can help ensure your system is running in tip-top condition!

Frequent maintenance checks will ensure that all components of your air conditioning system are in good working order. Your technician will clean or replace clogged air filters, check the thermostat settings, and inspect the refrigerant levels to make sure they are sufficient for efficient cooling. Your technician will verify that both the indoor and outdoor units are getting power, examine the expansion valve for any faults, and ensure the condensing unit is unblocked and functioning correctly.

Regular maintenance can not only prevent issues like your air conditioner blowing warm air but also extend the lifespan of your system, improve its efficiency, and lower your energy bills. Moreover, The Otter Guys’ team of professionals can spot potential problems early on, preventing costly repairs or system breakdowns in the future.


Regular maintenance can prevent many of the issues that lead to your air conditioner blowing warm air. By understanding the potential causes and working with a trusted professional like The Otter Guys, you can ensure that your air conditioning system continues to provide the cool, comfortable environment you desire throughout the summer months.

Remember, take care of your air conditioner so that it can take care of you during those hot summer days. Trust in the expertise of The Otter Guys to keep your system running smoothly all year round. Give them a call today to schedule your next maintenance, repair, or installation visit and experience the difference that professional care can make for your home’s comfort and your peace of mind.

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