AC Troubleshooting: Home Air Conditioner Starts Cold Then Gets Warm

image of a man feeling hot and uncomfortable due to ac blowing warm air

Consistent performance is a key expectation from air conditioners. They should effectively cool your house and maintain the desired temperature. However, if your system deviates from this normal process, it is important to investigate the underlying cause. For instance, if your home air conditioner initially provides cold air but gradually becomes warm over time, it is a cause for concern. This situation can be particularly frustrating when you rely on your unit for comfort and relief during the summer. This article discusses this common AC issue – the home air conditioner starts cold then gets warm.

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AC Troubleshooting: Home Air Conditioner Starts Cold Then Gets Warm

Air conditioners are designed to provide consistent cold air and should only stop once the temperature reaches your desired thermostat setting. It is unusual for the AC unit to suddenly start blowing warm air. If you experience a situation where your air conditioner initially blows cold air but then transitions to warm air, it indicates that something is amiss. This article will cover the common reasons behind this cooling system issue. It is crucial not to ignore this problem. Contacting an HVAC technician promptly is advised to address and resolve the issue.

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Most Common Reasons For A Cooling Unit To Blow Warm Air

Thermostat Malfunctions & Incorrect Settings

image of a homeowner adjusting thermostat due to air conditioner problems

The thermostat helps control the air conditioning system. It senses the environmental conditions and regulates the activity of the air conditioner to maintain the desired temperature. 

If you are experiencing issues with warm air blowing from your cooling system, make sure that the thermostat is functioning properly. Check the thermostat settings to see if they have been adjusted or programmed incorrectly. Sometimes, someone may have changed the settings inadvertently. The thermostat could be malfunctioning due to a low battery charge. Checking and addressing these factors can help identify and resolve the issue of warm air coming from the air conditioner.

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Missing or Dirty HVAC Air Filters

When air filters become excessively dirty, they prevent airflow through the air conditioner. This strains the blower and other components of the system, accelerating wear and tear and reducing overall efficiency. Similarly, if the filters are missing, dirt, allergens, and pollutants can freely enter the cooling system, causing potential damage. Accumulated dirt around the evaporator coils acts as an insulator, impeding thermal transfer and further decreasing efficiency. Sometimes, this can even lead to the unit freezing up. Regularly clean or replace air filters and maintain cleanliness around the evaporator coils to ensure optimal performance and prevent unnecessary strain on the air conditioning system. It also helps improve indoor air quality.

Lack of Air Filter Maintenance

image of a dirty air filter for home hvac system

Proper maintenance of air filters is essential to ensure their optimal performance. Over time, air filters become less effective, so you must replace them before they become a hindrance rather than an asset. This is a simple job that the average Joe can easily perform. How frequently you need to replace your filter depends on the level of usage and other factors. In a typical family home, checking the filter every month is advisable. Some homes may require a new filter every two months, while homes with multiple pets might need monthly replacements. For vacation homes that are rarely occupied, a filter replacement every six months may be sufficient. By regularly monitoring and replacing air filters, you can maintain a clean and efficient HVAC system.

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Low Air Conditioner Refrigerant

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The refrigerant plays a vital role in the operation of an air conditioner. It is the key component for transferring heat from the house to the outside. As warm air circulates through the system, the refrigerant cools the home during each cycle. Maintaining an adequate refrigerant level for the air conditioner to function effectively is vital. However, if there is a refrigerant leak, the amount can decrease, reducing efficiency and strain on the cooling system’s performance. Address refrigerant leaks promptly to ensure optimal functioning and efficiency of the air conditioner.

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Dirty or Damaged HVAC Ductwork

In central air conditioning systems, blowers are crucial in distributing cold air throughout the house via ductwork. However, if the ducts become damaged, problems can arise. Damaged ductwork can cause cold air to leak out, preventing it from reaching all rooms effectively. As a consequence, the farthest rooms may no longer receive the desired cooling; instead, hot air may be expelled from the compromised ducts. Damaged ductwork strains the system, forcing it to work harder to maintain the desired performance. This increased workload leads to accelerated wear and tear, potentially resulting in the need for premature replacement of the air conditioner. Address any duct damage promptly to ensure optimal cooling performance and system longevity.

Dirty or Frozen Air Conditioner Evaporator Coils

air conditioner coil

The evaporator coils capture heat from inside the home. When these coils become excessively dirty, their ability to perform effectively is compromised. Dirty coils inhibit heat transfer from the indoor air to the refrigerant flowing inside the coils. This can lead to various issues, including freezing up of the coils. If left unaddressed, the situation can worsen over time. To prevent this, clean the evaporator coils regularly. Maintaining clean coils ensures efficient heat transfer and avoids problems associated with frozen or inefficient coils. Regular coil cleaning is an essential maintenance task to keep your air AC unit running smoothly.

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Air Conditioning Electrical Problems

Be vigilant about electrical issues in your air conditioning system. Insufficient power supply to specific components can trigger a chain reaction, leading to the undesirable outcome of warm air emitted from the air conditioner blower. So make sure that all components receive adequate power and that there are no disruptions in the electrical connections. Regular maintenance and timely inspections by a qualified technician can help identify and address any electrical problems before they affect can the performance of your air conditioning system.

How To Avoid Unnecessary Issues With Your Cooling System

Replace Air Conditioner Air Filters Regularly

Sufficient airflow is crucial for the optimal functioning of your air conditioner. The primary hindrance to proper airflow is dirty HVAC filters. Replace these filters regularly to maintain efficient airflow. In a typical family home, replacing the filters every three months at the maximum is recommended. However, for added caution, replacing them every two months is advisable. If you have pets, who tend to shed hair and dander, it is best to replace the filters every month to ensure clean and unrestricted airflow throughout your home.

Schedule Annual Air Conditioner Maintenance

image of an hvac contractor performing an air conditioner tune-up

In preparation for the summer season, thoroughly clean your house, especially in the springtime. Schedule annual professional air conditioner maintenance during this period. This proactive step ensures that your system is fully prepared for the upcoming demands of summer. Skilled technicians can identify and address any potential problems promptly, preventing further damage. They will also clean and lubricate the cooling system, promoting smoother and more efficient operation. These maintenance measures enhance comfort, reduce energy costs, and extend the system’s lifespan.

Keep the Air Conditioner Condenser Clear of Plants & Debris

Be mindful of dirt and debris accumulation to prevent clogs in your outdoor unit. Take proactive measures such as regularly trimming the plants around the unit and ensuring a 2-foot distance between the unit and any greenery. Inspect the top of the unit and remove any debris that may have been collected, such as dried leaves and twigs. You can sweep them away or manually remove them to maintain a clean and unobstructed outdoor unit.

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What To Do When Your AC System Is Blowing Warm Air

If your AC is blowing warm air, identify the potential causes and pinpoint the issue. After you have identified the issue, take appropriate steps to resolve it. However, if the issue persists or you are still trying to figure out the solution, contact an HVAC company immediately. Prompt intervention can prevent the problem from escalating into a more significant issue. It is always more cost-effective to address the problem early rather than risking the need for a complete HVAC system replacement due to long-term neglect.


Air conditioners are designed to generate cold air, so if you notice warm air coming out of your system, immediately take action. Begin by troubleshooting the issue using basic troubleshooting techniques. If you can’t identify or resolve the issue, seek the assistance of professional HVAC experts. Taking immediate action can prevent further breakdowns of your cooling system and save you from the expense of costly replacements.

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At Miller Oil Company, we take pride in offering top-notch heating and cooling services to residents in the greater Enfield, Connecticut area. Our team comprises highly skilled and certified technicians specializing in HVAC tune-ups, repairs, installations, replacements, and more. With their extensive knowledge, training, and experience, you can trust them to provide exceptional service for your HVAC system.

Our company is committed to providing our clients with the most competitive prices for heating and cooling services in the region. Our maintenance services are designed to enhance your comfort and energy efficiency, reducing energy costs for your home. Whether you require HVAC repairs or a replacement system, our experts will guide you in selecting the best option that suits your requirements and budget.

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