• Smart AC
    • Sensibo Sky

      Smart AC Control

    • Sensibo Air

      Next-Gen Smart AC Control

    • Sensibo Air Pro

      The world’s #1 Smart AC Control

    • Sensibo Air + Room Sensor

      For improved home automation

  • Smart Air Quality
  • Accessories
    • Room Sensor

      For improved home automation

    • Shield AC Filters

      For improved home automation

    • Pure Filters

      Subscribe for auto-renewal

  • Plans
  • About Sensibo

    About Sensibo

    Bringing smart management of indoor climate to your home or business

  • Our Impact

    Our Impact

    Mitigating climate change & making an impact around the world.

  • Our Blog

    Our Blog

    Read insights from the leaders in smart air conditioning & indoor air quality solutions

  • Careers


    Check out our open positions

  • Support & FAQ

    Support & FAQ

    Need help? Check out our FAQs or reach out to our team

  • Press


    The essential resource hub for press

  • Investors


    Invest in the Future of Sustainability and AI

  • Contact Us

    Contact Us

    We’re here to help. Reach out and let’s chat

  • News


    Latest news and press releases from Sensibo

  • Affiliate Program

    Affiliate Program

    Promote green living and earn with Sensibo’s affiliate program

    • Senisbo Air Pro selected as TIME 2023 Best invention Special Mention

Why is the air conditioner running but not cooling? 7 common problems

7 minute read

HEPA filter

As the scorching heat of summer bears down upon us, the humble air conditioner becomes a lifeline, cooling the house and providing us with a refreshing escape from the oppressive temperatures. We rely on these cooling air conditioning systems to create a comfortable indoor oasis where we can seek refuge and relax. However, there are few things more frustrating than when your air conditioner seems to be running incessantly, yet fails to deliver the expected cooling relief.

From minor issues such as thermostat settings and airflow problems to more complex concerns like refrigerant leaks and compressor malfunctions, we will explore each potential cause and its corresponding solutions. By understanding these common problems, you'll be better equipped to diagnose the issue and determine whether you can tackle it yourself or require the expertise of a professional technician.

So, let's embark on a journey through the inner workings of your air conditioner, uncovering the mysteries behind its lackluster cooling performance. By the end of this article, you'll be armed with the know-how to beat the heat and restore your cooling system to its full potential. Remember, a little knowledge and proactive maintenance can go a long way in ensuring your air conditioner keeps you blissfully cool all summer long.

Room in yellow

Thermostat Settings and Airflow Issues

1. Thermostat Settings: One of the most common and easily overlooked reasons for an air conditioner running but not cooling effectively is incorrect thermostat settings. Ensure that your thermostat is set to the appropriate cooling mode and set at the desired temperature. Sometimes, accidental changes or a misunderstanding of the thermostat's settings can lead to the air conditioner not providing the desired cooling comfort.

Solution: Double-check your thermostat settings to ensure it is set to "Cool" mode and at the temperature you want. If your thermostat is programmable, review the schedule to ensure it aligns with your cooling needs throughout the day.

2. Obstructions and Blocked Vents: Proper airflow is crucial for effective cooling. Blocked or obstructed vents can restrict the flow of cooled air into your living spaces, leading to uneven cooling and reduced performance. Obstructions can include furniture, curtains, or any items placed in front of vents that hinder the airflow.

Solution: Inspect all the vents in your home to ensure they are not obstructed. Clear away any objects that may be blocking air filters from the vents, allowing unrestricted airflow of warm indoor air. Also, ensure that the return air vents are free from obstructions to facilitate proper air circulation.

3. Dirty Air Filters: Air filters play a crucial role in maintaining good indoor air quality and efficient airflow through your air conditioning system. Over time, these filters can become clogged with dust, dirt, and debris, restricting the airflow and making it harder for the air conditioner to cool your home effectively.

Solution: Check your air filters regularly and replace them as needed, typically every 1 to 3 months or as recommended by the manufacturer. Clean filters promote better airflow, improve cooling efficiency, and help maintain a healthier indoor environment.

Comfortable room

Refrigerant Leaks and Low Levels

Refrigerant is a vital component in the cooling process of an air conditioner central ac system. It is responsible for absorbing heat from the indoor air and releasing it outside, facilitating the cooling of indoor spaces. If there's a refrigerant leak or insufficient levels, the air conditioner ac system's cooling performance will be severely affected.

Detecting refrigerant leaks is crucial to resolving cooling issues. Some signs of a refrigerant leak include:

  • Reduced Cooling Performance: Your air conditioner may not cool your home as effectively as it should.
  • Hissing Sounds: You might hear a hissing or bubbling noise, indicating a refrigerant leak.
  • Icing on the Coils: Refrigerant leaks can lead to ice formation on the evaporator coils, hindering proper cooling.

When refrigerant levels are low due to leaks, the whole air conditioner not cooling it's performance suffers:

  • Inadequate Cooling: Low refrigerant levels prevent the air conditioner from absorbing enough heat, leading to insufficient cooling.
  • Compressor Strain: The compressor may work harder to compensate for the low refrigerant levels, increasing the risk of damage or failure.
  • Increased Energy Consumption: A struggling air conditioner uses more energy as it tries to maintain cooling, leading to higher utility bills.
    Refrigerant-related issues require professional attention due to their complexity and safety concerns. If you suspect a refrigerant leak, contact a licensed HVAC technician immediately. They will locate and repair the leak, test the system for proper refrigerant charge, and recharge it if necessary.

Dirty or Frozen Evaporator Coils

The evaporator coils are an integral part of the air conditioning system, responsible for absorbing heat from the indoor air. As warm air passes over these coils, the refrigerant inside them absorbs the heat, transforming the heat pump the air into cool, comfortable temperatures before circulating it back and blowing air into your living spaces.

Over time, dust, dirt, and other airborne particles can accumulate on the evaporator coils. This layer of debris acts as an insulating barrier, preventing cold air blowing the coils from absorbing heat effectively. As a result, the cooling efficiency of outdoor coil of your air conditioner significantly diminishes.

Woman in the comfortable room

When the evaporator coils are dirty, several problems arise:

  • Reduced Cooling Efficiency: The buildup of dirt on the coils inhibits their ability to absorb heat from the air, leading to a decrease in cooling performance.
  • Longer Cooling Cycles: The air conditioner compensates for the reduced cooling efficiency by running longer, resulting in increased energy consumption.
  • Frost Formation: In severe cases, the dirt on the coils can cause the coils to become excessively cold, leading to the formation of frost or ice. This further hampers the heat exchange process and worsens cooling performance.

Solutions for Dirty Evaporator Coils: To address dirty evaporator coils, regular maintenance is crucial:

  • Cleaning: Schedule regular professional maintenance to clean the evaporator coils and remove any accumulated dirt and debris.
  • Air Filters: Replace or clean air filters regularly to minimize the amount of dirt reaching the coils.
  • Duct Cleaning: Ensure that your ductwork is clean and free from dust and debris, reducing the likelihood of dirt reaching the coils.

Faulty Compressor

The compressor is the heart of ac unit of the air conditioning system. It is heat pump system is responsible for pressurizing the refrigerant, allowing it to circulate between the evaporator coils (indoors) and the condenser coils (outdoors). This process enables the refrigerant to absorb and release heat, making the cooling of indoor air possible.

A faulty compressor can be caused by various factors:

  • Electrical Problems: Issues with electrical connections or components can prevent the compressor from receiving the necessary power to function correctly.
  • Motor Malfunctions: Motor problems, such as a seized motor or worn-out bearings, can lead to compressor failure.
  • Overheating: The compressor can overheat due to a lack of proper ventilation or insufficient refrigerant levels.

Consequences of a Faulty Compressor: A malfunctioning compressor results in significant cooling problems:

  • Inadequate Cooling: A faulty compressor cannot efficiently circulate refrigerant, leading to poor cooling performance.
  • Noisy Operation: If the compressor is struggling or experiencing mechanical issues, it may produce unusual and loud noises.
  • Increased Energy Consumption: An overworked or malfunctioning compressor consumes more energy, contributing to higher utility bills.
    Repairing or replacing a faulty compressor is a complex task that requires professional expertise. If you suspect a problem with the compressor, it is best to contact a licensed HVAC technician. They will diagnose the issue, assess whether repairs are possible, or recommend a replacement if necessary.

Inadequate Sizing or Insulation

The size of your air conditioner is a critical factor that directly impacts its cooling efficiency. If your air conditioner is too small for the space it's intended to move cool air to, it will struggle to keep up with the demand, resulting in inadequate cooling. Conversely, an oversized unit will cycle central the air conditioner on and off frequently, failing to remove humidity effectively and leading to discomfort.

Open window

Having an air conditioner that is improperly sized for your home can lead to various issues:

  • Inefficient Cooling: An undersized unit will struggle to cool your home adequately, leaving certain areas uncomfortably warm.
  • Constant Operation: An undersized air conditioner might run continuously, trying to meet the cooling demand, which increases energy consumption and wears out the components faster.
  • Short Cycling: Oversized units tend to short cycle, turning on and off frequently, leading to increased wear and tear on the system.

Solutions for Inadequate Sizing: To ensure your air conditioner is properly sized:

  • Consult with a Professional: Seek the advice of a qualified HVAC technician to determine the appropriate size of air conditioner for your home based on factors like square footage, insulation, and climate.
  • Replace or Upgrade: If your current air conditioner is inadequately sized, consider replacing it with a properly sized unit to achieve optimal cooling efficiency.
  • Importance of Insulation: Insulation plays a crucial role in maintaining a comfortable indoor environment. Proper insulation helps retain the cooled air, preventing heat gain from the outside, and supports the air conditioner's cooling efforts.

Dirty Condenser Unit

The condenser unit is located outside your home and plays a crucial role in releasing the heat absorbed from indoor air by the refrigerant. It facilitates the heat exchange process with outdoor units, allowing the refrigerant to cool down and prepare ac system for another cycle of heat absorption.

As the condenser unit is exposed to the outdoor environment, it is susceptible to accumulating dirt, leaves, grass clippings, and other debris. This buildup creates a barrier, reducing the unit's ability to release heat energy effectively.

Room and the table

Consequences of a Dirty Condenser Unit: A dirty condenser unit can lead to cooling problems:

  • Inadequate Heat Release: The accumulated debris acts as an insulating layer, inhibiting the release of heat from the refrigerant.
  • Reduced Cooling Efficiency: When the condenser unit cannot release heat efficiently, the air conditioner's overall cooling efficiency decreases.
  • System Overheating: An overworked air conditioner due to a dirty condenser unit may lead to system overheating, causing breakdowns or malfunctions.

Solutions for a Dirty Condenser Unit: To maintain proper airflow through the condenser unit and ensure proper heat exchange:

  • Regular Cleaning: Keep the area around the condenser unit clear of debris, and regularly clean the unit itself to prevent dirt buildup.
  • Professional Maintenance: Schedule professional maintenance to clean the condenser coils and ensure the unit is in optimal condition for efficient cooling.

Electrical and Wiring Problems

The electrical system of your air conditioner is vital for powering the air conditioning unit and its various components, including the compressor and fan motors. Proper electrical connections ensure smooth operation and cooling performance.

Electrical problems can occur due to factors like loose connections, damaged wires, or faulty capacitors. These issues disrupt the flow of electricity, leading to irregular functioning or total system failure.

Electrical and wiring problems can cause significant cooling issues:

  • Erratic Functioning: Inconsistent cooling cycles or intermittent operation can result from faulty electrical connections.
  • System Shutdown: Serious electrical issues may lead to complete system shutdown, leaving your home without cooling.

Solutions for Electrical and Wiring Problems: Handling electrical components requires expertise, so it's crucial to seek professional assistance:

  • Professional Inspection: Schedule regular maintenance visits with a qualified HVAC technician to inspect and address any electrical problems.
  • Prompt Repairs: If you notice any irregularities or suspect electrical issues, have them promptly addressed by a licensed technician to prevent further complications.


When your air conditioner runs but fails to deliver the refreshing coolness you expect, it can be frustrating and uncomfortable, especially during scorching summer days. In this article, we explored some of the most common issues with your central air conditioning system that can cause this cooling conundrum and provided insights into possible solutions.

From simple problems like thermostat settings and airflow issues blowing cold and blowing warm air out, to more complex issues such as refrigerant leaks, dirty evaporator coils, faulty compressors, inadequate sizing, dirty condenser units, and electrical problems, we delved into the various culprits behind the lackluster cooling performance of air conditioners.

Summer room

The key takeaway is the importance of regular maintenance and attention to your air conditioning system. Simple tasks like checking and adjusting thermostat settings, ensuring proper airflow through unobstructed vents, and replacing dirty air filters can go a long way in preventing cooling issues and maintaining air ducts peak performance.

Additionally, addressing more complex issues, such as refrigerant leaks or compressor malfunctions, requires the expertise of qualified HVAC technicians. DIY attempts at handling refrigerant-related problems can be dangerous and may result in more significant issues, so it's best to leave these tasks to the professionals.

Furthermore, proper sizing of your air conditioner and adequate insulation from cold air also contribute significantly to cooling efficiency. Consult with an HVAC expert to ensure your air conditioner is appropriately sized for your home, and invest in proper insulation to maintain room temperature air for a comfortable indoor environment and minimize energy waste.

Lastly, keeping the condenser unit clean and free from debris is essential for efficient heat exchange and cooling performance. Regular professional maintenance of outdoor condenser unit and fan, including condenser coil cleaning, will help prevent issues arising from a dirty condenser unit.

Shop sensibo Smart Products
Once upon a time any A/C became smart sensing

The device that pays for itself. Maximize comfort and savings

Sign up & save 5% on your first order!

Stay up to date on the latest sales, product releases & news