A temperature sensor, such as a thermistor, senses the temperature inside a power source connector, or other portion, of a power supply. This sensed temperature may then be used to determine if the output power should be reduced or switched off in order to avoid overheating of the connector, or other portion of the power supply. Overheating of the power supply may occur, for example, if contact between the connector and a cigarette lighter power receptacle is incomplete. A microcontroller may be used to monitor the temperature sensed by the temperature sensor and reduce or disable the power supply if the temperature is above a threshold temperate. Accordingly, heat damage to the plastic components of the power supply, the cigarette lighter receptacle, may be reduced.