It's one of the most frustrating problems in summer: your AC is running, but the room just won't cool down. Here are the three most common causes and what you can do about them.

1. Low Refrigerant (Gas Leak)

Refrigerant is the chemical that absorbs heat from your room. If the level is low due to a leak, cooling performance drops significantly. Signs include ice forming on the unit and a hissing sound. This requires a professional to detect the leak, repair it, and recharge the system.

2. Dirty Air Filter or Coil

A clogged filter restricts airflow, preventing the system from exchanging heat efficiently. The evaporator coil can also ice up due to reduced airflow. Clean or replace your filter monthly. If the coil is iced, turn the AC to fan-only mode for a few hours to thaw it.

3. Failing Compressor

The compressor is the heart of your AC. When it starts failing, cooling performance drops gradually. Signs include the outdoor unit running but the indoor unit not cooling, or the outdoor unit not starting at all. Compressor replacement is expensive but necessary.