The supplemental PTC heater in the Ford Escape is a part of the Cold Weather Package. PTC specifically stands for Positive Temperature Coefficient. It is an electrical heater that is self-regulating as opposed to relying on wires. They usually made of either ceRamic or a special type of rubber. Instal lation of this heater allows hot air to blow through Your vents immediately upon starting the car instead of having to wait for the engine to warm when in very cold environments. It is located in the A/C plenum box. Other features included in this Package are heated seats, heated side mirrors, weatherized floor mats, and a windshield wiper de-icer.