Air conditioners are a blessing, especially during the hot summer months. They provide a much-needed reprieve from the heat by cooling our homes and offices. However, there are times when you turn on your air conditioner, only to find that it’s running but not cooling. This issue can be frustrating, but don’t worry—there are several potential causes, and most of them can be fixed with some troubleshooting. If you’re experiencing this problem, here’s a guide to help you understand why your air conditioner might not be cooling and how to fix it.
1. Check the Thermostat Settings
The first thing you should do when your air conditioner is running but not cooling is check the thermostat settings. Sometimes, a simple error like setting the thermostat to “Heat” instead of “Cool” can be the culprit. Verify that the thermostat is set to the cooling mode and that the temperature setting is lower than the current room temperature.
Additionally, if your thermostat is set to a temperature that’s too high or has been adjusted incorrectly, the air conditioner may not be able to cool the space effectively. Set the thermostat to the desired temperature and ensure that it’s functioning properly.
2. Replace the Air Filter
One of the most common reasons an air conditioner runs but doesn’t cool effectively is a clogged or dirty air filter. When the filter is blocked with dust, dirt, or other debris, it restricts airflow, making it harder for the unit to cool the air properly. Restricted airflow can lead to inefficient cooling or even a system freeze-up.
To fix this, turn off the power to your air conditioner and remove the air filter. Inspect it for dirt and grime. If it’s dirty, clean it with warm water or replace it with a new one if it’s beyond cleaning. Air filters should generally be replaced every 1–3 months depending on usage and the type of filter. Ensuring a clean filter will improve the airflow and help your air conditioner run more efficiently.
3. Inspect the Refrigerant Level
Refrigerant is the substance that absorbs heat from the air inside your home and cools it before circulating it back into the room. If your air conditioner is low on refrigerant, it won’t be able to cool effectively. This can happen due to a refrigerant leak or because the unit was undercharged during installation.
To check the refrigerant level, you’ll likely need to call a professional HVAC technician, as they have the proper tools and knowledge to handle refrigerants safely. If the refrigerant is low, the technician will identify and fix the leak, then recharge the system with the correct amount of refrigerant.
4. Clean the Condenser Coils
Your air conditioner has two main coils—the evaporator coil (inside the unit) and the condenser coil (outside). The condenser coil plays a vital role in releasing the heat absorbed from your home. If the condenser coils are dirty or covered with debris like leaves, dirt, or grass, the air conditioner won’t be able to release heat effectively, causing it to run but not cool properly.
To fix this, turn off the power to the unit and inspect the outside condenser coil. Use a hose to gently clean the coils, removing any debris or dirt. Be careful not to bend the fins. You can also use a special coil cleaner to deep clean the coils if necessary. Cleaning the coils ensures that the air conditioner can release heat and cool your home properly.
5. Check for Frozen Evaporator Coils
Another common issue with air conditioners that run but don’t cool is frozen evaporator coils. The evaporator coil is responsible for absorbing heat from the air. However, when the airflow is restricted (due to a dirty filter, low refrigerant levels, or other issues), the coils can freeze up. When this happens, the air conditioner may blow warm air or fail to cool the room properly.
If you notice that the air coming out of the vents is warm, and the unit is running for an extended period, check the evaporator coil. You can do this by turning off the unit, allowing the ice to melt, and then inspecting the coil. Once the coil has thawed, make sure that the airflow is unimpeded and clean the air filter to ensure that no debris is blocking it.
6. Inspect the Ductwork for Leaks or Blockages
The ductwork that carries cool air from your air conditioner into your home can sometimes become damaged or obstructed, leading to poor airflow. If you notice that your air conditioner is running but not cooling, check for any leaks or blockages in the ductwork.
Leaks in the ducts allow cooled air to escape before it reaches the rooms in your home, while blockages can stop air from circulating properly. Inspect the ducts in accessible areas for any visible signs of damage. If you find leaks, use duct tape or sealant to patch them. If you suspect blockages or need further assistance, consider hiring a professional to clean and inspect the ducts.
7. Check the Outdoor Unit
Sometimes the problem might lie with the outdoor unit, which is responsible for expelling heat from the refrigerant. If the outdoor unit is obstructed by debris or has malfunctioned, it can prevent the system from cooling properly.
Turn off the power to the unit and inspect the outdoor condenser unit. Ensure that the area around the unit is clear of debris, leaves, or anything that could obstruct airflow. Check the fan for proper movement and listen for any unusual noises that might indicate a problem.

8. Examine the Compressor
The compressor is one of the most important components of an air conditioner. It helps to compress and circulate the refrigerant throughout the system. If the compressor is malfunctioning, the air conditioner may run but not cool effectively. This is a more serious issue that usually requires professional attention.
If you suspect the compressor is the problem, it’s best to call a qualified HVAC technician. They can test the compressor and repair or replace it if necessary.
9. Consider the Age of the Unit
If your air conditioner is old, it may not be cooling efficiently even if all components are functioning properly. Air conditioners generally last between 10–15 years, depending on usage and maintenance. After this period, the system may begin to lose its efficiency, and repairs may become more frequent.
If your unit is approaching the end of its lifespan, it might be time to consider replacing it. An energy-efficient model could save you money in the long run by cooling your home more effectively and using less energy.
10. Professional Help
If you’ve gone through all these troubleshooting steps and your air conditioner is still running but not cooling, it’s time to call in a professional. HVAC technicians have the training and tools to diagnose and repair complex issues that may be preventing your air conditioner from cooling properly. In such cases, seeking aircon servicing Boon Keng can be an excellent option to ensure your system is checked and repaired efficiently by experts.
Conclusion
Dealing with an air conditioner that’s running but not cooling can be frustrating, but with some basic troubleshooting, you can often fix the problem yourself. Start by checking the thermostat settings, replacing the air filter, and inspecting the refrigerant level and coils. If the problem persists, you may need to clean the condenser, check the ductwork, or call a professional. With regular maintenance and timely repairs, you can keep your air conditioner running efficiently and enjoy a cool, comfortable home all year long.