North Carolina Home Inspector Practice Exam

What is the most likely cause of ice forming on an A/C evaporator coil?

1. Low refrigerant levels

2. Not enough air

3. Defective thermostat

4. Faulty compressor

The correct answer is: Not enough air

The formation of ice on an A/C evaporator coil is most commonly caused by insufficient airflow over the coil. When air doesn't circulate properly, it prevents the coil from absorbing heat effectively. This lack of airflow can occur for various reasons, such as a dirty air filter, blocked ducts, or a malfunctioning blower fan. When warm air is unable to flow across the cold coil, the moisture in the air condenses and freezes on the coil, leading to icing. While low refrigerant levels and other system malfunctions can contribute to performance issues, they tend to lead to other symptoms and are less directly connected to the specific phenomenon of ice formation due to airflow problems. The thermostat and compressor also play important roles in the system's overall function but are not the primary causes of ice buildup on the evaporator coil. Understanding the significance of airflow helps in diagnosing and resolving issues related to air conditioning systems effectively.