What would be indicated by frost on the evaporator core?

Frost on the evaporator core is typically an indication of a restriction in the core. When there is a restriction, the flow of refrigerant is impeded, leading to a drop in pressure and temperature in that area. As the temperature of the evaporator core drops significantly, it can cause the moisture in the air passing over it to freeze, resulting in frost formation.

This frost can lead to ice accumulation, which could limit air flow and reduce the efficiency of the air conditioning system. It suggests that the refrigerant is not circulating properly or that there is an obstruction that prevents it from adequately absorbing heat, an essential function of the evaporator core. Understanding this helps technicians diagnose issues with the HVAC system effectively, preventing further complications.