Abstract: A method and apparatus are provided for indicating the status of the refrigerant charge in an air conditioning system based upon the degree of subcooling present in the condensed refrigerant system temperature measurements. The status of the refrigerant charge in the system is indicated in real-time on a service panel for access by a field service technician. The status of the refrigerant charge in the system on a time-average basis for a specified period of operation is presented on an indicator panel. The indicator panel includes a first indicator light indicating that the refrigerant charge is low, a second indicator light indicating that the refrigerant charge is high, and a third indicator light indicating that the refrigerant charge is correct.