Low refrigerant charge detection system

Abstract

An apparatus for detecting is disclosed for detecting a low level of refrigerant circulating through a motor vehicle refrigerant circuit. The apparatus comprises an electronic logic module, and a pressure transducer and a thermistor preferably located in the refrigerant circuit between the compressor and the evaporator. The pressure transducer generates a signal indicative of the refrigerant pressure, from which the module derives a saturation temperature of the refrigerant. The saturation temperature is compared with the measured temperature to determine if a superheat condition exists indicative of low refrigerant charge exists. When the refrigerant remains at a predetermined level of superheating, the compressor clutch is disengaged to interrupt circulation through the refrigerant circuit. In an alternative embodiment, a pair of thermistors are respectively situated proximate an inlet and an outlet of an evaporator, and the module interrupts circulation when the outlet thermistor indicates a temperature more than a predetermined amount greater than the inlet thermistor. In a third embodiment, a pressure switch in the refrigerant circuit generates a signal when a predetermined pressure is reached, and the module interrupts circulation if the temperature of the medium at the predetermined pressure corresponds to a superheat condition.

Dependencies are inferred from the claim text.