Due to the requirement of cost and development time reduction all automotive OEMs and suppliers need to increase their productivity. At the same time the number of electrical systems in a modern vehicle runs into hundreds, and the design and optimization of the wire-harness connecting all components together is becoming a significant design task. Optimizing the cost and the quality of the harness for satisfactory operation under a wide range of conditions is important to keep the vehicle cost competitive. The use of a simulation tool to help in wire sizing and test, tightly coupled to a dedicated harness design tool is getting indispensable for this task.The different components will be integrated together with the harness on a virtual platform. With this concept it is possible to perform functional tests or to do FMEA quite early in the design cycle. The paper will show the development process from the first functional schematics over the cabling diagram, down to the manufacturing data in a bundle drawing. Furthermore it will bridge the gap between 2D CAD and 3D Mechanical CAD. The design of a Power Window System will serve as a demonstrator for this new development flow.