One reason for an air conditioner not cooling: insufficient refrigerant (also known as "snow seed" insufficient).

This is a normal situation, typically seen in air conditioners that are three to four years old. The air conditioner doesn't completely fail to cool, but the cooling effect is insufficient. This is because 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 Two for Air Conditioner Not Cooling: Insufficient Voltage Supply

Unstable power supply voltage often fails to reach normal levels, especially during peak usage hours. Of course, this issue is clearly beyond the capabilities of a technically proficient air conditioner repairman. We must address the problem by ensuring a stable power supply.

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

Reason 3 for Air Conditioner Not Cooling: Insufficient Power Rating

This is also one of the common reasons for non-cooling, but the causes for this non-cooling can be diverse, such as: 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 adequately sealed (like open doors and windows), or the presence of heat sources inside the room (such as multiple computers), of course, the western exposure of glass houses is also one of the heat sources, etc.