Audi 80/Avant (B4)

since 1991-1995 of release

Repair and car operation

Audi 80/Avant
+ Technical specification
+ Engines
+ System of production of the fulfilled gases
+ cooling System
+ Fuel tank and fuel pump
+ Air filter and airintaking channels
+ injection System
+ Coupling
+ Transmission and transmission
+ Suspension bracket and steering
+ Brake system
+ Anti-blocking system of brakes
+ Wheels and tires
- Body electrosystem
   Minus to "weight"
   Orientation in electrosystem
   Plug connections
   Central switchboard
   Additional block of the relay
   Relay and control units
   Unloading relay of contact X
   Safety locks
   Table of safety locks
   Electric circuits
   + Full electroscheme of the Audi 80 car: 2-liter 4-cylinder engine (66 kW)
   + 2-liter 4-cylinder engine (85 kW)
   + 2,3-liter 5-cylinder engine (98 kW)
   + 2,6-liter 6-cylinder engine (110кВт)
   + Additional equipment
   + Storage battery
   + Generator
   Check of a condition of a maple or polilinovy belt
   Tension of a maple belt
   Tension of a maple or poliklinovy belt
   Torn maple a belt
   Engine overheat because of damage of a maple belt
   Review of maple and poliklinovy belts
   Replacement of a maple belt
   List of malfunctions
   List of malfunctions
+ ignition System
+ Lighting
+ Signalling devices
+ Devices and auxiliary devices
+ Heating and ventilation
+ body Elements
+ Search of malfunctions
+ Specifications

Relay and control units

Look under a back seat of Audi 80 of the version a sedan

1–control unit differential blocking (only all-wheel drive models);
2–switch of longitudinal acceleration of anti-blocking system (only all-wheel drive models);

3–control unit anti-blocking system;
4–additional block of the relay.

On an illustration on the additional block of the relay (2) under a back seat of a sedan of Audi 80 the double relay (1) anti-blocking system is necessary. This relay can be used in the cars equipped as appropriate and as by the relay of protection against an overstrain of system of inclusion of a safety cushion. On the same place it is possible to put and the relay of electronic blocking of differential (EDS). The nearby cell 21 in sedans usually remains empty. In the following cell 20 the relay of a screen wiper of back glass of the versatile person of Audi 80 is inserted. In a cell 19 (near outer side of the car) the relay of shutdown of the back fog lights, established on models, with a factory complete set the traction coupling device (turnbuckle) is located.

A number of the relay and the control units located in the central switchboard or on the additional block of the relay at the left under the dashboard or under a back seat belongs to onboard electrosystem.

The simple switching relay is applied first of all to powerful consumers of a current. It has the following basis: if to carry out a food on long cable lines via the corresponding switches, tension losses will be a consequence. Besides, contacts of switches are exposed to big loading because of a bigger current. At the relay scheme the switch is used only for a low current, the consumer of a current, and its relay is thus connected not directly.

If the switching team arrives not from the switch, and from the control unit, the same picture: sensitive electronic elements cannot carry out big currents without damage to themselves.

  • Certain relays can carry out additional functions. So, the relay of the index of turn includes blinking impulses, and the relay of system of washing of glasses and a screen wiper operates faltering action and work without screen wiper water after washing of glasses.
  • Control units are supplied with more or less difficult electronic systems for certain functions, sometimes in them the relay is established also. As an example it is possible to call the control unit electric window regulators or the control unit of a delay of shutdown of light in salon.

Principle of operation of the switching relay

  • At inclusion of the corresponding consumer of a food in the relay the electric chain from the plug 86 (arriving «a switching current») to the plug 85 (case) becomes isolated.
  • Thanks to it an electromagnet, overcoming resistance of a spring, draws powerful contact and thus closes an electric chain for «a working current».
  • For prevention of losses of tension the working current is carried out on the shortest way directly to the plug of 30 relays and from there further – under condition of the closed contacts via the plug 87 to the consumer of a food.
  • Sometimes the plug 87 meets also and. It is rigidly connected with the plug 87, that is carries out the same function.

Search of malfunctions of switching relays


  1. On the plug 30 always there should be a tension, in that case if speech does not go about the relay which consumer depends on other consumer. Example: tension on the relay of a back antifog lamp moves only if is turned on the light.
  2. For stock-taking of tension to take to (put forward) the relay and to touch with a needle electrode of a control bulb the plug 30 in a relay socle. Lack of tension means a rupture of a wire.
  3. To remove the relay, the plug 86 to connect to a positive pole of the storage battery, and the plug 85 with the case ("weight"). The coil of an electromagnet should (is clearly audible) to draw relay contact, otherwise the relay is faulty.

The help at the defective switching relay


  1. To take out the relay from a nest.
  2. To connect plugs 30 and 87 in a relay cell by means of a writing paper clip or a short slice of a wire. Thanks to it the corresponding consumer will receive a direct current.
  3. For shutdown to remove this crossing point as the corresponding switch in this case is bypassed.

On the removed cover (7) central switchboards in a short form (6) are displayed a possible arrangement of the relay and safety locks. In the same place there are small plastic flat-nose pliers for a detachment of safety locks. In the central switchboard various relays (1), tips for diagnostic devices (2), safety locks 1–21 (3), and also additional safety locks 23-32 (4) are visible. Further four spare safety locks (5) are placed.