What is a common sign of low refrigerant levels in a system?

Frost on the evaporator is a common sign of low refrigerant levels in a system because when the refrigerant is insufficient, it cannot effectively absorb heat from the surrounding air. This leads to a drop in temperature on the evaporator coil, causing moisture in the air to condense and freeze on the coil itself. As the frost builds up, airflow can become restricted, further hindering the cooling process and potentially leading to system failure if not addressed. Recognizing this symptom is crucial for diagnosing refrigerant issues, as maintaining the correct refrigerant level is essential for optimal system performance and efficiency.