What condition indicates that a refrigeration system may not be functioning properly?

Frost buildup along the evaporator coil is a clear indicator that a refrigeration system may not be functioning properly. This condition often suggests that there is an issue with airflow or that the system is experiencing low refrigerant levels. In a properly operating refrigeration system, the evaporator coil should maintain an appropriate temperature to allow for the efficient absorption of heat from the surrounding air, resulting in even cooling. However, if frost begins to accumulate, it means that the coil is likely not able to expel heat effectively, which can lead to reduced efficiency and potential operational issues.

Other signs, such as normal suction pressure, even cooling throughout the evaporator, and consistent compressor operation, do not indicate a malfunctioning system. Normal suction pressure typically suggests that the system is maintaining the expected pressure levels for efficient refrigerant flow. Even cooling across the evaporator indicates that the distribution of cooling is functioning well, and consistent compressor operation generally suggests that the system is cycling as expected without any interruptions. Thus, the presence of frost signifies a potential problem, making it the correct choice in this context.