Home AC units

Common Reasons Your Home AC Unit Isn’t Cooling Effectively

Is your AC unit struggling to provide the cool and comfortable environment you desire in your home? It can be incredibly frustrating when your AC unit fails to effectively cool your house, especially during hot summer months. Fortunately, there are common reasons why this may be happening and understanding these factors can help you identify and resolve the issue.

home ac unit

In this article, we will explore the common reasons why your AC unit may not be cooling your house effectively. Whether you have a newly installed central air system or have been relying on your AC unit for years without any issues, it’s important to be aware of potential problems that can arise. Maintaining your air conditioning unit should not just be for summer, but a regular maintenance task to ensure it works properly throughout the whole year.

From neglecting regular maintenance to encountering blocked ducts or damaged ductwork, we will discuss these factors and more, providing you with insights and practical solutions to restore the cooling efficiency of your AC unit. By understanding these common issues, you’ll be better equipped to address the problem and ensure a comfortable and refreshing indoor environment for you and your family.

Regular Service from a Licensed HVAC Company

First and foremost, if your not getting regular servicing on your AC unit then it’s important to arrange a visit as soon as possible. Scheduling regular maintenance helps your central air unit operate effectively.

Neglecting regular maintenance and running your unit for extended periods without professional servicing can lead to various problems. By having an HVAC company technician perform the necessary tests and checks during these service calls, you significantly reduce the risk of unexpected breakdowns and ensure the longevity of your central air unit’s performance.

HVAC technician cleaning

How often should I have my AC unit serviced?

The frequency of servicing your AC unit can vary depending on factors such as the manufacturer’s recommendations, the age of the unit, and your specific usage patterns. However, as a general guideline, it is recommended to have your AC unit professionally serviced at least once a year.

Having an annual service ensures that your AC unit receives necessary maintenance, inspections, and cleaning to keep it running smoothly and efficiently. This typically includes tasks such as checking refrigerant levels, cleaning or replacing filters, inspecting electrical components, lubricating moving parts, and evaluating overall system performance.

If you live in an area with prolonged hot seasons or if you use your AC unit extensively, it may be beneficial to schedule maintenance twice a year, with intervals of approximately six months. This can help address any potential issues and ensure optimal performance during peak usage periods.

Ultimately, it’s best to consult with a HVAC company technician who can assess your specific circumstances and provide personalized recommendations on the ideal servicing frequency for your AC unit.

AC unit maintenance

What is completed during an AC unit service?

During an AC unit service, an HVAC technician typically performs a range of tasks to ensure the proper functioning and efficiency of the system. While specific procedures may vary depending on the company and the type of unit, the following are common activities included in an AC unit service:

  1. Inspection: The technician will visually inspect the AC unit, checking for any visible signs of damage, wear, or leaks. They will also assess the overall condition of the components.
  2. Filter Cleaning/Replacement: The technician will clean or replace the air filters to ensure proper airflow and to maintain good indoor air quality. Installing a high-quality air filter is believed to be the best solution out there for maintaining your air conditioning unit. Consider inquiring from AC inspection services in your locality and they can recommend the best AC filter to use. 
  3. Coil Cleaning: The evaporator and condenser coils will be inspected and cleaned. Over time, these coils can accumulate dirt, debris, and dust, reducing the unit’s efficiency. Cleaning them helps optimize cooling performance.
  4. Refrigerant Level Check: The technician will measure the refrigerant levels in the system to ensure they are within the manufacturer’s recommended range. If necessary, they may add or remove refrigerant to achieve the correct levels.
  5. Condensate Drain Cleaning: The condensate drain line will be checked and cleaned to prevent clogs or blockages, which can lead to water leaks or system malfunctions.
  6. Electrical Components Inspection: The technician will inspect electrical connections, wiring, and components such as capacitors and relays to ensure they are in good condition and functioning correctly.
  7. Lubrication: Moving parts such as motors and fans may require lubrication to reduce friction and ensure smooth operation.
  8. Thermostat Calibration: The thermostat will be checked and calibrated if needed to ensure accurate temperature control and efficient operation.
  9. System Performance Evaluation: The technician may perform tests to assess the overall performance of the AC unit, including temperature differentials, airflow measurements, and system efficiency.
  10. Recommendations and Maintenance Tips: After the service, the technician may provide recommendations for any necessary repairs, improvements, or upgrades. They may also offer maintenance tips to help you keep your AC unit in good condition between service visits.

How to check your AC unit for faults and issues

Check for blocked air ducts

The cool air generated by your AC unit is delivered to different areas of your home through ductwork. Although the ductwork is not visible throughout the house, you can see it in the basement as it runs behind walls and ceilings.

AC duct access

To experience the desired cooling effect, your home should have vents in every room. This ensures consistent airflow and maintains cool air temperatures when your central air unit is running.

However, if you notice that certain rooms are not receiving cool air, it is likely due to blocked ducts. To determine if this is the issue, you can perform some of your own visual checks. Open up vents and where accessible to try and identify a cause for the blockage. If you are unable to see any signs it is recommended to contact a commercial AC repair team who can inspect the ducts.

There are various reasons for duct blockages. For instance, you may have a loose duct caused by playful children who have inserted objects like clothing or toys into the ductwork. Alternatively, animals such as mice might be using the ductwork for nesting, which usually does not lead to severe blockages. However, if you have raccoons or possums creating nests, it can result in significant obstructions.

Removing these pests is crucial before your AC unit can function properly again. By addressing the blockages and eliminating any unwanted inhabitants, you can restore the optimal functioning of your AC system.

home ac ducting

Damaged Ductwork

In some cases, you might notice that certain rooms or zones in your house are not receiving cool air despite your AC unit functioning correctly. When your AC unit is working as it should be, you can shift your attention to the ductwork to investigate if it is causing the problem.

Damaged ductwork is often the reason why cool air fails to reach specific areas of your home. Additionally, during colder weather, warm air may struggle to reach those same areas due to the damaged ducts.

Instances of ductwork deterioration are more common in older houses with aging duct systems. For example, if you have a HUD property that has remained vacant for an extended period, you may discover damaged ductwork that requires repair to optimize your HVAC performance.

While there can be other issues affecting the effectiveness of your central air unit, consulting a reputable HVAC company is usually the best approach. They possess the expertise to diagnose the problem accurately. Once the issue is identified, appropriate measures will be taken to resolve the situation and restore the efficient operation of your AC system.

Dirty air filters

Dirty air filters can significantly impact the cooling effectiveness of your AC unit. Over time, air filters can become clogged with dust, dirt, pollen, pet dander, and other airborne particles. When the filters are obstructed, the airflow through the system is restricted, leading to reduced cooling efficiency.

dirty vs clean air filter

Air filters should be changed as part of your annual service, however you can complete this task quite easily yourself. Here’s a quick guide:

  1. Locate the air filter: The air filter is usually located in the return air duct or the air handler unit of your AC system. It may be behind a removable grille or panel.
  2. Turn off the AC unit: Before removing the air filter, it’s important to turn off the AC unit to prevent any potential damage or injury.
  3. Remove the old filter: Slide out the old filter from its slot carefully. Take note of its size and orientation for the replacement.
  4. Check the condition of the filter: Inspect the old filter for dirt, dust, or damage. If it’s dirty or clogged, it’s definitely time for a replacement.
  5. Install the new filter: Take the new filter and insert it into the slot, making sure it fits securely. Align it correctly based on the directional arrows or markings on the filter.
  6. Close the access panel or grille: Once the new filter is in place, securely close the access panel or grille that covers it.
  7. Turn on the AC unit: Finally, you can turn the AC unit back on and enjoy improved airflow with the new, clean filter in place.

It’s worth noting that different AC units may have slight variations in their filter replacement process, so it’s always a good idea to consult the manufacturer’s instructions or refer to the user manual specific to your AC unit for detailed guidance. If you’re uncertain or uncomfortable with performing the task yourself, you can also seek assistance from an HVAC professional.

Other factors affecting your AC Unit performance

Here are a few more reasons why you AC unit might not be functioning at it’s best.

Oversized or Undersized AC Unit

If your AC unit is not appropriately sized for your home, it can lead to inefficiencies. An oversized unit may cool the space too quickly without effectively removing humidity, resulting in a clammy environment. Conversely, an undersized unit may struggle to cool the entire space adequately. Consulting with an HVAC professional to determine the right-sized unit for your home is crucial.

As a general rule here is a table showing the BTU size unit required for the square footage of your home.

Square FootageRecommended BTU
Up to 1505,000 – 6,000
150-2506,000 – 7,000
250-3007,000 – 8,000
300-3508,000 – 9,000
350-4009,000 – 10,000
400-45010,000 – 11,000
450-55011,000 – 12,000
550-70012,000 – 14,000
700-1,00014,000 – 18,000
1,000-1,20018,000 – 21,000
1,200-1,40021,000 – 23,000
1,400-1,50023,000 – 24,000
1,500-2,00024,000 – 30,000
2,000-2,50030,000 – 34,000
2,500-3,00034,000 – 38,000
3,000-4,00038,000 – 48,000
4,000 and up48,000 and above

Dirty Condenser Coils

The condenser coils in the outdoor unit of your AC system play a crucial role in transferring heat from inside your home to the outside environment. Over time, these coils can accumulate dirt, dust, and debris, which creates a barrier and obstructs the heat transfer process. This accumulation can significantly impact the efficiency and cooling performance of your AC unit.

condenser coils in AC unit

To determine if your condenser coils are dirty, you can perform a visual inspection. Start by turning off the power to the AC unit. Then, locate the outdoor unit and remove any debris, such as leaves or grass clippings, from the surrounding area. Carefully examine the condenser coils for visible dirt, dust, or debris buildup. If you notice a layer of grime covering the coils, it’s an indication that they need cleaning.

Cleaning the condenser coils is a task you can undertake yourself, although it requires caution and some basic tools. Begin by using a soft brush or a handheld vacuum cleaner with a brush attachment to gently remove loose debris from the coils.

condenser coil cleaning brushes eBay

Take care not to bend or damage the delicate fins on the coils. Next, use a coil cleaner specifically designed for air conditioner coils. Follow the manufacturer’s instructions to apply the cleaner, typically by spraying it onto the coils and allowing it to penetrate the dirt and grime. After a few minutes, rinse the coils thoroughly with water using a hose or a pressure washer on a gentle setting. Additions such as UV lighting can be installed to prevent the build-up of bacteria or mould around cooling coils. You can read more about how UVC lights can benefit your HVAC installations here.

It’s important to note that cleaning the condenser coils is recommended as part of regular maintenance, typically on an annual basis or as needed. However, if you’re uncomfortable performing this task or if the coils are heavily soiled, it’s best to seek professional assistance from an HVAC technician.

Issues requiring professional help

The following issues, in most cases, will require professional help to resolve.

Low Refrigerant Levels

The refrigerant in your AC system is responsible for absorbing heat from the indoor air. If the refrigerant levels are low due to leaks or other issues, the cooling capacity of the unit will be affected. A professional HVAC technician can identify and repair refrigerant leaks and recharge the system if needed.

Faulty Thermostat

A malfunctioning thermostat can cause inaccurate temperature readings, leading to improper cooling. It may result in the AC unit not running long enough or not cooling enough. Checking and calibrating the thermostat or replacing it if necessary can help resolve the issue.

Insufficient Insulation

Poor insulation in your home can allow cool air to escape and warm air to enter, reducing the effectiveness of your AC system. Insulating your home properly, especially in attics, walls, and windows, can improve energy efficiency and cooling performance.

Electrical Issues

Faulty wiring, tripped breakers, or other electrical problems can prevent the AC unit from operating properly. It’s important to have an electrician or HVAC technician inspect the electrical connections and address any issues that may affect the cooling efficiency.


Understanding the common reasons why your AC unit may not be cooling your house effectively is crucial for maintaining a comfortable indoor environment. By addressing these issues promptly, you can optimize the performance and efficiency of your air conditioning system. Remember to schedule regular maintenance with a licensed HVAC company to ensure that your unit receives proper care and attention.

From checking and replacing dirty air filters to cleaning the condenser coils, there are several tasks you can perform yourself to improve your AC unit’s functionality. However, it’s essential to exercise caution and seek professional assistance when needed to avoid any potential damage or safety risks.

Taking proactive measures, such as maintaining clean air filters, ensuring unobstructed airflow, and keeping the condenser coils free from dirt and debris, will help your AC unit operate at its best. These simple steps can enhance cooling efficiency, prolong the lifespan of your system, and ultimately provide you with a comfortable and enjoyable indoor environment.

Remember, if you encounter persistent issues or your AC unit requires extensive repairs, it’s always wise to consult a qualified HVAC technician. They possess the knowledge, skills, and tools necessary to diagnose and resolve complex problems effectively.

By prioritizing regular maintenance, performing basic checks, and addressing any issues promptly, you can ensure that your AC unit continues to provide optimal cooling performance and keeps your home comfortable throughout the seasons. Stay cool and enjoy the benefits of a properly functioning air conditioning system!

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