Designation of parts on schematic diagrams, colors of wires (Audi A4 B6)

Table of contents: Metal parts: grounding contact ↓ Colors and numbers ↓ Main colors and purpose of wires ↓

Schematic diagrams help to understand the intricacies of electrical wires and parts. When using these diagrams, it is best to first find the corresponding part in the legend. The most important design elements are designated by the following letters, which are supplemented by clarifying numbers:

Letter designation	Structural element
A	battery
IN	starter
WITH	three-phase current generator
D	ignition and starter switch
E	manual control switch
F	mechanical switch
G	sensor, control device
N	sound signal (simple sound signal, two-tone sound signal, etc.)
J	relay, control device
K, L, M, W, X	signal lights, lamps, lighting fixtures
N	electric valves, resistors, switching devices
ABOUT	distributor
P, Q	spark plug tip, spark plug
R	radio
S	fuse
T	detachable connections
V	electric motors

Most consumers are connected by two wires. However, it is often possible to trace the passage of only one wire from the consumer to the battery or generator. The second wire is screwed to the body, engine or gearbox after a few centimeters, or connected to the contact tongue.

Metal parts: grounding contact

Metal parts, which in electrical engineering are called mass, are capable of conducting current, which allows you to save on wires. Instead of laying a wire to the negative pole of the battery, the case is used as this wire. If some consumer does not work, then this is often due to the fact that it is not connected to the mass. Sometimes a simple connection to the case is not enough, in this case an additional wire is laid, which, as a rule, is brown.

Colors and numbers

The Audi A4 has a large number of wires, but the confusion of wires only seems so at first glance: the wires are marked with color, most of the connections to the connectors and relays are numbered. The numbering is done according to DIN standards. Additional numbers are used for identification on white wires. The designation of the terminals is also standardized. Some of the most important terminals are:

Terminal 30. Battery voltage is always applied to this terminal. The wires are usually red or red with colored stripes.
Terminal 31. Connects to ground, usually via a brown wire.
Terminal 15. Power is supplied to this terminal through the ignition switch. Current flows through the wires connected to this terminal only when the ignition is on. The wires are usually green or green with colored stripes.
Terminal X. This terminal supplies power to increasingly powerful consumers, such as high beam lamps. Current flows through the terminal when the ignition is on, but when the starter is activated, the current is interrupted. This allows the ignition system to receive full battery voltage.

Main colors and purpose of wires

The wires are red. Pos current flowing from the positive terminal of the battery or generator (with the engine running). If the negative battery cable is not disconnected, careless handling of tools may result in a short circuit or sparks.

The wires are black. Current to black wires; is supplied through the ignition switch when the ignition is on, and, with the exception of the ignition and fuel injection system, power is supplied only to those consumers that should be supplied with power only when the vehicle is in operation.

The wires are brown. These wires are used for direct connection to the ground. In order for the circuit to be closed, current consumers must be connected to the body via black (not brown) wires.

The wires are grey. They are used for power supply circuits of side, rear and parking lights, as well as for power supply of the license plate light.

In addition, the following colors are used to designate wires: blue, yellow, green, purple, orange and white.

The numbers that can be seen on the circuit diagrams next to the wire color designation indicate the wire cross-section. If the wire is connected to a plug connection (T), the combination of numbers indicates the type of connection and the contact point: