Chill with Confidence: Ace the 2026 ASE Air Conditioner Exam and Keep Cool Under the Hood!

Excessive frost on the evaporator is a clear indication of either a low refrigerant charge or an airflow restriction. When the refrigerant charge is low, it leads to a drop in pressure within the evaporator, which can cause the temperature to drop significantly, resulting in frost formation. Proper airflow is essential for the evaporator to function effectively; if there is a restriction—possibly due to a clogged cabin air filter or issues with the blower motor—air cannot pass over the evaporator as intended. This also contributes to the temperature drop and subsequent frost buildup as the refrigerant cannot absorb heat effectively.

In contrast, a high refrigerant charge would typically lead to higher pressures in the system, which could prevent frost formation on the evaporator. High ambient temperature may affect the overall performance of the AC system but is not directly responsible for frost formation on the evaporator specifically. Insufficient car battery power could affect the operation of the AC system but does not have a direct relationship with excessive frost on the evaporator. Understanding the conditions under which frost appears helps diagnose issues and maintain proper air conditioning functionality.