Understanding European DIN wiring

Motor,  Apr 2003  by Seyfert, Karl

• E-mail
• Print
• Link

European wiring diagrams may look strange and incomprehensible. But they're not so tough to understand when the underlying standards are explained.

Over the years, I've heard many explanations for why some technicians choose not to work on European vehicles. For some, it's based on their desire to work only on vehicles built within our borders. For others, the choice may be based on the belief that European cars are just too "foreign" and their systems too unusual or exotic to easily understand.

In today's automotive economy, it has become increasingly difficult to hold onto these attitudes. Many cars sold in this country by European (and Asian) manufacturers are actually assembled right here in the U.S. This blurs the conventional definition of an imported vehicle. At the same time, many "American" cars are actually assembled outside our borders, further confusing the accepted definition of a domestic car.

Auto manufacturing is truly a global enterprise, with all of the major manufacturers conducting business in several countries simultaneously. Even if we ignore the differences of language and culture, isn't it still a difficult problem for a European manufacturer to build vehicles in a different country like the U.S.? To oversimplify the challenges involved, how do you get an American assembly line to crank out parts for a European car? The answer is standards. Standards have been an integral part of the automotive world since the earliest days of the automotive assembly line. Standardization of parts allowed automakers to transform their businesses from a one-at-a-time proposition to a many-at-a-time operation.

In this country, the Society of Automotive Engineers (SAE) is responsible for maintaining order by establishing many of the standards that apply to automobile manufacturing. When you pick a bolt for a domestic vehicle out of the bolt bin, chances are the standards and specifications concerning its thread pitch and hardness were originally defined by SAE. Thanks to standardization, that bolt should thread into any nut made anywhere in the world, as long as it conforms to the same set of standards.

In Europe, the most widely recognized organization responsible for establishing and publishing automotive standards is called Deutsches Institut fur Normung e.V Standards established by this organization are often referred to as DIN standards.

DIN standards have been established for a multitude of things, including many outside the automotive world, but we'll limit the focus of this article to the DIN standards for automotive wiring. Why wiring? Because that's the one thing I've heard the most techs complain about when it comes to working on European vehicles. For some, it's the layout of the electrical components throughout the vehicle. For others, it's understanding the wiring diagrams that map out the position and operation of all those systems and components. The diagrams may look strange and incomprehensible. But when you understand the underlying system and standards that were used to design the vehicles and the diagrams, it's not as tough as it first seems.

Terminal Designations

DIN standard 72 552 establishes the terminal numbering system that's used for any wiring diagram or vehicle wiring that conforms to DIN specifications. The terminal codes are not wire designations, as devices with differing terminal codes can be connected to the opposite ends of a single wire. The chart on pages 42 and 43 outlines many of the common terminal designations described under DIN 72 552. Some of the more obscure numbers, which refer to components on trailers, heavy-duty trucks and such, have been intentionally omitted.

When you've worked with DIN wiring for a while, you'll begin to recognize certain numbers that come into play more often than others. For example, a terminal 31 designation always refers to a direct connection to vehicle ground and a terminal 30 designation always represents a direct connection to the battery positive terminal. And terminal 50 is always battery positive with the key ON or in the CRANK position.

Wire Color Codes

Before we get into some actual DIN wiring diagrams, a word about wire color codes. Most wiring diagrams you're likely to come across will have already been translated into English. Wire colors in those diagrams should be labeled with abbreviations you'll be able to understand. But just in case you run across a diagram with the original wiring color codes, use the "Wire Colors" key at left to sort things out. By the way, color codes for electrical wiring are defined in DIN 47 002.

Circuit, Block & Schematic Diagrams

Description of an electrical system or circuit may begin with a circuit diagram. This is an idealized representation, rendered in the form of symbols to provide a quick overview of circuit and device functions. The circuit diagram illustrates the functional interrelationships and physical links that connect various devices. These diagrams may also include illustrations and simplified design drawings, as needed.