The evaporator fan plays a crucial role in maintaining indoor air quality by circulating air through the evaporator coil, where heat exchange occurs. A malfunctioning fan can lead to reduced airflow, allowing pollutants and allergens to accumulate in the living space. This can exacerbate respiratory issues and create unpleasant odors. Proper operation of the evaporator fan ensures that air is circulated and filtered, maintaining a healthy indoor environment.