The invention relates to a plug assembly for a small refrigerating unit or the like which plug assembly is equipped with one or more PTC resistors. Thermally loaded, ceramic resistors such as PTC resistors are generally brittle and have the characteristics of a substantial temperature expansion coefficient while being relatively weak structurally. The plug assembly accommodates one or more PTC resistors with a resistor holding device in which resiliently biased electrical contacts hold the resistors firmly in fixed positions while permitting the resistors to expand freely upon being heated without incurring stresses which would cause breakage.