RE: Checking Refrigerant Charge
It is very easy to tell when a refrigerator with a standard evaporator has the correct charge of refrigerant by the total area of frost on the evaporator. If 100% of the evaporator has frost on it, the refrigerant charge is adequate. As refrigerant is lost, the frost will disappear on part of the evaporator. An overcharge of refrigerant will result in frost outside the box on the line returning to the compressor. This method of measuring refrigerant charge is not accurate enough for best performance when adding refrigerant.Frost line method for determining refrigerant charge cannot be used on holding plate systems.