Commercial Refrigeration Certification Practice Test

When the evaporator fan motor is stopped in a refrigeration system, air circulation within the evaporator is halted. This leads to an increase in temperature within the display case because the cooled air is not being distributed effectively throughout the space. The evaporator's primary function is to absorb heat from the refrigerated space, and the fan plays a crucial role in ensuring that the cool air produced is circulated evenly.

Without the operation of the fan, the temperature can rise significantly, as the warm air from the display case isn't being replaced with cooler air, and the heat exchange process is compromised. This disruption can also lead to other issues, such as increased humidity and possible product spoilage over time.

In contrast, the other options suggest effects that do not occur due to the fan motor stopping. For example, freezing of the evaporator typically occurs when airflow is restricted or when the system is operating in a specific malfunctioning state, but stopping the fan immediately leads to poor air circulation rather than freezing. An increase in cooling efficiency and defrosting also cannot occur in this scenario, as both require active air movement and proper system operations to work effectively.