What happens to the suction vapor if the fins on the evaporator become blocked?

When the fins on the evaporator become blocked, the flow of air over the evaporator coils is restricted. This leads to a decrease in the heat exchange capability of the evaporator, which results in less heat being absorbed from the refrigerant inside the coils.

As the airflow diminishes, the suction vapor that enters the evaporator can no longer effectively absorb the heat, causing the temperature of the refrigerant to drop. Consequently, since the suction vapor is not able to absorb enough heat energy, the pressure within the evaporator also tends to decrease as the refrigerant struggles to evaporate properly.

This combination of reduced heat absorption and inadequate vaporization results in both lower pressure and temperature of the suction vapor. Therefore, the correct answer reflects the understanding that blocked fins limit the efficiency of the evaporator, leading to downward shifts in pressure and temperature in the refrigerant cycle.