What could be a cause of a partially iced over evaporator?

A partially iced over evaporator is often a result of an undercharge of refrigerant. In a refrigeration system, refrigerant plays a crucial role in absorbing heat and maintaining proper airflow across the evaporator coils. When there is an undercharge, there is insufficient refrigerant to absorb the necessary heat from the air passing over the coils. As a result, the temperature of the remaining refrigerant can drop too low, causing moisture in the air to freeze on the evaporator coils and lead to partial icing.

This condition can inhibit airflow and reduce the efficiency of the air conditioning system. By ensuring that the refrigerant charge is appropriate, the system can operate effectively, avoiding issues like icing while promoting proper heat exchange.

In contrast, fluctuating humidity levels could contribute to icing under certain circumstances but are less likely to be the primary cause than a refrigerant charge issue. Excessive refrigerant flow might lead to other complications in the system, like flooding, but not typically icing specifically. High ambient temperatures could affect system performance but would not directly lead to a state of partial icing in the evaporator coils.