ESCO Air Conditioning Practice Exam 2025 – The All-in-One Guide to Exam Success!

Icing on the evaporator coils of an AC unit can primarily be caused by low refrigerant levels or inadequate airflow. When the refrigerant level is low, there may not be enough fluid to absorb heat effectively, leading to a drop in pressure and temperature at the evaporator coils. This allows moisture in the air to freeze on the coils, forming ice.

Inadequate airflow can also contribute to icing; if the air cannot circulate properly through the evaporator coils due to obstructions or poor fan performance, the coils can become too cold and start to freeze moisture. Therefore, a combination of low refrigerant levels and restricted airflow creates conditions that lead to ice formation on the coils, hindering the air conditioner's ability to function effectively.

While the other choices could be problems in an air conditioning system, they do not directly lead to icing on the evaporator coils. High refrigerant levels typically do not cause icing; rather, they could lead to other performance issues. Overheating components might suggest an overall malfunction but would not specifically result in icing on coils. Lastly, dirty filters can restrict airflow, which is a contributing factor, but without addressing refrigerant levels, the core issue of icing may not be resolved.