Abstract: An auxiliary power port such as is found in an automotive vehicle passenger compartment has a receptacle connected with the vehicle electrical system and a tubular, removable sleeve which fits inside the receptacle and receives a standard adapter plug of the type intended for use with automotive power ports. The exterior surface of the sleeve is covered with a layer of positive temperature coefficient (positive temperature coefficient) material, and insertion of the sleeve into the receptacle places the positive temperature coefficient layer in contact with the inner surface of the receptacle. The inner surface of the receptacle, the outer surface of the sleeve, and the positive temperature coefficient layer sandwiched therebetween form a positive temperature coefficient circuit overcurrent protection device. A number of interchangeable sleeves having different hold currents are provided for use with different electrical devices.