Structure and inner electrical connection

Resistors with a positive temperature coefficient (PTC) are designated as PTC resistors. The warmer the PTC becomes, the higher its resistance. With a PTC, high current flows at switch on, for example. With increasing heating, this level of current falls. Metals are PTC conductors. Their resistance increases with rising temperature.

Fig 1: Engine Ventilation Heating - Circuit Diagram

Courtesy of BMW OF NORTH AMERICA, INC.

Pin assignments 

The engine ventilation heating is supplied by the junction box with terminal 15N. The Digital Diesel Electronics (DDE) activate the engine ventilation heating on the ground side.