How do you read a wiring diagram?

A wiring diagram uses symbols, letters and codes, which are often understood by the technical person. You can read a wiring diagram if you know and understand the symbols, which are many. You should also know the color coding for the wiring as well as the meaning o the various letters and symbols for the components to be used. You can find more information here: http://www.bentleypublishers.com/images//tech/VW/vw.wiring.diagram.pdf