Split air conditioners are among the most widely used cooling systems due to their high efficiency and independent cooling performance. However, one of the most common issues users face is a noticeable drop in cooling capacity over time. This problem can arise from several factors. Some are simple to fix, while others require a professional technician’s intervention. In this article, we will review the most important causes of reduced cooling performance in air conditioners.
This article explores the main reasons behind reduced cooling in split air conditioners and discusses possible solutions.

Improper Capacity Selection
Choosing an air conditioner with an inappropriate capacity for the space is one of the main reasons for weak cooling. Capacity is measured in BTU/hr, and if a low-capacity AC is installed in a large room, the unit will be forced to run constantly. This not only reduces cooling efficiency but also shortens the lifespan of the system due to overwork. Selecting the correct capacity based on room size and cooling load is essential.
Refrigerant Leakage or Low Levels
Refrigerant is the core element in the cooling process. It absorbs heat indoors through the evaporator and releases it outdoors via the condenser. If refrigerant levels drop due to leaks or improper charging, the cooling capacity decreases significantly. Leaks may occur in pipes, fittings, or connections. The system should be checked for oil stains or pressure loss. The best solution is to call a licensed technician to repair leaks and recharge the refrigerant.
Clogged or Dirty Air Filters
Indoor unit filters are designed to trap dust and airborne particles. Over time, these filters clog and restrict airflow, reducing cooling efficiency. Clogged filters may also cause coil icing, further blocking air circulation. Cleaning filters every three months with lukewarm water or replacing them when necessary is a simple and effective maintenance step.
Unsuitable Installation Location
The installation site of both indoor and outdoor units greatly affects performance. The outdoor condenser should not be placed under direct sunlight or in a closed, poorly ventilated area, as this disrupts heat exchange. Proper distance between indoor and outdoor units must also be maintained. Correct installation enhances efficiency and prolongs the unit’s lifespan.
Compressor Issues
The compressor is the heart of the AC system. Its role is to compress the refrigerant and circulate it through the evaporator and condenser coils. Any malfunction, such as overload, electrical faults, or faulty sensors, can disrupt this process, resulting in poor cooling or total system failure. Compressor repairs are complex and must be handled by a qualified technician.
Dirty Condenser Coils
The outdoor condenser coils release heat into the outside air. When dust, dirt, or debris accumulate on the coils, they act like insulation and block proper heat dissipation. As a result, the cooling performance drops significantly. Regular cleaning of the coils with air pressure or washing ensures optimal operation.
Faulty Blower Fan
The blower fan in the indoor unit distributes cooled air into the room. If the fan is malfunctioning, even a properly cooling system won’t deliver enough airflow to the space. Issues may arise from electrical or mechanical faults. Professional inspection is required to diagnose and fix the problem.
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Thermostat Malfunction
The thermostat regulates room temperature by controlling the compressor. If it is faulty, the system may switch on and off incorrectly, leading to inconsistent or weak cooling. Sometimes the issue comes from poor wiring, while other times the thermostat itself must be repaired or replaced.
Additional Factors
In addition to the main causes above, other issues may also reduce cooling efficiency:
- Pipe or connection leaks: cause refrigerant pressure to drop.
- Excessive dirt around the outdoor unit: prevents proper airflow.
- Electrical issues or faulty wiring: disrupt overall system function.
Though less obvious, these factors are often the hidden reason behind reduced performance.
Reasons Why Air Conditioner Doesn't Work Effectively in Brief
Reduced cooling in split air conditioners is a common but preventable issue. Key causes include improper capacity selection, low refrigerant levels, dirty filters and coils, poor installation, compressor or fan problems, and thermostat faults. Regular maintenance, cleaning, and proper installation can prevent most of these issues. For more serious issues, contacting a licensed technician is the safest and most effective solution to restore your air conditioner’s performance.
Now that you are familiar with the main reasons why an air conditioner may fail to cool properly, we recommend visiting the DamaTajhiz Professional Magazine to find expert answers from trusted sources for all your questions about HVAC equipment.
DamaTajhiz is a specialized company in the production and supply of cooling and heating systems, which started its professional activity in 2004.
In the DamaTajhiz specialized platform, you can compare different types of air conditioners, ducted split units, fan coil units, cooling towers, chillers, mini chillers, water heaters, heaters, water filters, and more. After reviewing their specifications and prices, you can easily choose and purchase the best option.
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