Heat Transfer
WARNING: This page is about a different car, the 2017 Volkswagen Touareg, 2016 Volkswagen Touareg, and 2015 Volkswagen Touareg. However, it is still accessible from the selected car via links, so may be relevant.
Every substance consists of a mass of moving molecules. The fast moving molecules of a warmer substance give off some of their energy to the cooler and thus slower molecules. As a result, the molecular motion of the warmer substance slows down and that of the colder substance is accelerated. This process continues until the molecules of both substances are moving at the same speed. They are then at the same temperature and no further heat exchange takes place.