ESCO Air Conditioning Practice Exam

Insufficient cooling accompanied by ice buildup on the evaporator coils is a primary symptom that indicates an air conditioning system is low on refrigerant. When the refrigerant level is low, the system cannot absorb enough heat from the indoor air, which leads to inadequate cooling performance. As the refrigerant circulates through the evaporator coils, the reduced pressure caused by the low refrigerant can lead to a drop in temperature, causing moisture in the air around the coils to freeze. This ice buildup further restricts airflow and hampers the system's ability to cool the space effectively, creating a vicious cycle of inefficiency.

The other options, while they can indicate various issues within an air conditioning system, do not specifically point to low refrigerant levels. Unusual noises may indicate mechanical problems, frequent cycling usually hints at a thermostat or electrical issue, and increased humidity typically relates to a malfunctioning system that could be due to multiple factors, not just low refrigerant. Thus, the specific pairing of insufficient cooling and ice formation is closely associated with refrigerant issues, making it the most accurate choice in this context.