If you want to detect a malfunction in the electrical system or install additional electrical components, then it is impossible to do without an electrical circuit. Guided by the diagram, you can detect the presence of electric current and wire connectors. The corresponding electrical circuit must be closed, otherwise there will be no electric current in it. It is not enough, for example, to supply voltage to the positive terminal of the headlight, if at the same time the electrical circuit is not closed through ground.
Therefore, the battery ground wire is also connected to the vehicle body. However, sometimes this earth connection is not enough, and the corresponding consumer is connected to earth directly by a wire, which is usually colored brown. Switches, relays, fuses, meters, electrical motors, or other electrical components may be connected in a separate electrical circuit. To be able to connect these parts correctly, the individual contacts are marked accordingly.
In order to visually order the interlacing of wires, at least on the electrical circuit, the individual current paths are arranged vertically next to each other and numbered.
The vertical lines come up to the mostly grayed out field. This field symbolizes the relay board with fuse holders and, at the same time, the positive connectors of the electrical circuit. First of all, there is also an internal ground wire on the relay board (terminal 31). Thin strokes on the field explain how and which electrical circuits inside the relay board are connected to each other. At the bottom, the electrical circuit line is connected to a horizontal line, symbolizing the connection to the car body. The ground connection is usually made directly through the body or through a wire from the ground connector located on the body.
When an electrical circuit ends with a square containing a number, this number indicates the number of the current line to which this electrical circuit is then connected.
In the description under the corresponding electrical circuit, its individual elements are named. The left column gives the abbreviated designation of the elements, consisting of a letter and a serial number containing from one to three digits. The right column contains the names of the elements.
Letter designations of the most important parts:
| Letter designation | Detail |
| A | accumulator battery |
| IN | starter |
| WITH | alternator |
| D | ignition and starter switch |
| E | manual switch |
| F | mechanical switch |
| G | sensor, control device |
| H | horn, two-tone horn, electromagnetic horn |
| J | relay, control unit |
| K,L,M,W,X | signaling devices, lamps, lanterns |
| N | solenoid valves, resistors, switches |
| 0 | distributor |
| P.Q | spark plug tips, spark plugs |
| R | radio |
| S | circuit breakers |
| T | plug connectors |
| V | electric motors |
For more accurate recognition, digital symbols are also added to the letter designations.
Relays and electronic control units are usually grayed out. The lines drawn inside them refer to internal wiring. They show how the relay and other electrical/electronic parts are connected both to each other and to the relay board.
The number in the black square indicates the location of the relay on the relay board with fuse holder. Directly at the indicated relay is the designation of the contacts.
Example: If the contacts are labeled 17/87 on the wiring diagram, then 17 is the terminal designation on the relay board and 87 is the terminal designation on the relay/control box. The designation of the terminals is given in accordance with the industrial standard of the Federal Republic of Germany (DIN).
The most important terminal designations:
Terminal 30. Battery voltage is always connected to this terminal. The wires are mostly red or red with colored stripes.
Terminal 31 connects to the mass. Ground wires are usually brown.
Terminal 15 powered through the ignition switch. Current flows through the wires only when the ignition is on. The wires are usually green or green with colored stripes.
Terminal X it is also powered only when the ignition is on, but the power is interrupted when the starter is turned on. This ensures that the ignition system receives full power from the battery during the engine start process. All significant current consumers are connected to this electrical circuit. High beam headlights are also supplied with current through this terminal. So when the main beam is on and the ignition is off, the parking lights are automatically switched on.
In the electrical diagram, individual wires have numbers with letter combinations below them.
Example:
The numbers show what cross section a given wire has, and the letters indicate its color. If the letter designation consists of two groups, as in the example, then the first group of letters indicates the main color of the wire (ws - white), and the second group is its complementary color (ge - yellow). Since it happens that wires of the same color are used in different electrical circuits, it is recommended to check the combinations of wire colors at the corresponding connection terminals. White wires additionally have a number for distinguishing, which is located under the color designation on the electrical diagram.
Wire color code:
- bl - blue
- br - brown
- ge - yellow
- gn - green
- gr - gray
- li - lilac
- or - orange
- ro - red
- sw - black
- ws - white
Wires that are connected to each other by means of single or multi-pin plug connectors, along with the letter «T» for the plug connector have an additional digital combination.
Example: T2p - male connector, 2-pin; T32/27 - Male connector, 32-pin, with contact point 27.
In the electrical diagram, all consumers and switches are shown in a state of rest. The changing current flow after closing the circuit breaker is illustrated by the example of a two-position circuit breaker:
If switch 01242 is pressed to the first position, then the current from terminal 82 flows through terminal 83. The second jumper also moves one position, but does not turn on. Only after pressing the switch to the second position, the second jumper connects the inner wire 82 to the wire 84, and now the current through the wire 84 is fed further. At the same time, through the internal connection in the switch, namely through the wire extending at right angles from wire 83, the current supplied when the switch was turned on in the first position continues to flow.
Attention: Fuses in holders, starting from position 23, are indicated on electrical diagrams with the number 223.
Location of electrical circuits
VW POLO with sheer rear from November 2002
Due to lack of space, all wiring diagrams for each model year cannot be reviewed. However, you can rely on the proposed wiring diagrams if your car model is a model of a different year, since the changes, as a rule, concern only a part of the wiring diagrams.
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