One common reason for air conditioners not cooling properly: insufficient refrigerant (also known as "snow seed" not enough).

This is a normal occurrence, typically seen in air conditioners that are three to four years old. The AC doesn't completely fail to cool, but its cooling performance is insufficient. This is due to the fact that older models use Freon as the refrigerant, which can evaporate over time. Additionally, there's a possibility of Freon leakage due to improper installation or inherent issues with the machine.

Reason #2 for Air Conditioners Not Cooling: Insufficient Voltage Supply

The unstable power supply voltage frequently fails to reach normal levels, particularly during peak electricity usage times. Of course, such an issue is clearly beyond the scope of a technically skilled air conditioner repairman. We must address the root cause by ensuring a stable power supply.

What to do if an air conditioner doesn't cool: Maintain a normal power supply voltage or choose a variable-frequency air conditioner. Why a variable-frequency air conditioner can solve the voltage issue can be found in the article "What Are the Benefits of Variable-Frequency Air Conditioners - A Comprehensive List of Advantages."

Three Reasons Why Your Air Conditioner Isn't Cooling - Insufficient Power Rating

This is one of the common reasons for no cooling, but the causes for this are diverse. For instance, a low-power air conditioner in a large room, or in some cases, the air conditioner's power seems to match the room size, but due to the room not being well-sealed (such as open doors and windows), or the presence of heat sources inside (like multiple computers), of course, the western sun exposure on a glass room is also a heat source, among others.