Air Conditioning Repair Certification (ETI) 2025 – 400 Free Practice Questions to Pass the Exam

When a system is experiencing an undercharge, one of the most noticeable symptoms is a partially iced over evaporator. This occurs because insufficient refrigerant prevents the evaporator coil from absorbing enough heat from the air being circulated through the system. As a result, the temperature of the coil drops too low, leading to moisture in the air condensing and freezing on the coil's surface. This ice buildup can restrict airflow further, exacerbating the cooling inefficiency.

Understanding the mechanics of refrigeration helps clarify this phenomenon. The evaporator coil relies on a specific amount of refrigerant to function effectively, as it evaporates and absorbs heat from the indoor air. When the refrigerant level is low, the coil does not receive adequate heat transfer, causing the temperature to plummet and subsequently leading to the formation of ice.

A clogged expansion valve can impact refrigerant flow, but it is not a direct indication of undercharging. Similarly, the outdoor unit freezing might suggest various issues, including airflow restrictions or issues with the compressor, rather than simply low refrigerant. Lastly, no airflow through the unit can point to a range of problems like a failed blower motor or blocked ducts, which are not directly related to refrigerant levels.