One reason why air conditioners fail to cool: insufficient refrigerant (also known as "snow seed" not enough)

This is a common 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 hours. Of course, this issue is clearly beyond the scope of a technically proficient air conditioning repairman. We must address the root cause by ensuring a stable voltage supply.

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

Reason #3 for Air Conditioners Not Cooling: Insufficient Power Rating

This is one of the common reasons for non-cooling, but the causes for this non-cooling are diverse, such as: small-capacity air conditioners in large rooms, and in some cases, although the air conditioner's power seems to match the room size, the room is relatively not airtight (e.g., open doors and windows), or there are heat sources inside the room (e.g., multiple computers), of course, the west-facing glass of a greenhouse is also a heat source, among others.