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
   Basic elements
   Malfunctions of ABS
+ Wheels and tires
+ Body electrosystem
+ ignition System
+ Lighting
+ Signalling devices
+ Devices and auxiliary devices
+ Heating and ventilation
+ body Elements
+ Search of malfunctions
+ Specifications





Basic elements

Hydraulic block

The hydraulic block (2) of anti-blocking system is located in a motor compartment behind at the left. If to remove a protective cover (1), the relay of electromagnetic valves (3) and the relay of the returnable pump (4) are visible.

It is located in a motor compartment at the left behind: the hydraulic block is between the brake pipeline from the main brake cylinder and the brake pipeline to wheel brakes. According to commands of the electronic control unit pressure in brake system is supported to constants, decreases or created again. However this pressure cannot be higher than that is created in the main brake cylinder after pressing of a pedal of a brake by the driver. Regulation of pressure is carried out by four quickly in with an electromagnetic drive – on one on a wheel.

If on valves a food does not arrive, pressure increases. At the maximum giving of a food there is a pressure decrease, at an average food pressure is supported to constants. The pressure decrease phase is especially interesting: as it is impossible to give to the brake liquid arriving from the main brake cylinder, it is simple to go to a receiver (differently thereof the brake pedal simply would fail), the powerful returnable pump pumps over brake liquid back to the main brake cylinder. You notice this process on a pedal of a brake which starts to pulse slightly if the returnable pump works, that is action is entered by ABS. If to listen, it is possible to hear and pump noise. The noise isolation in the hydraulic block slightly muffles sounds of operation of the pump.

Above on the hydraulic block two more relays are located along with shtekerny connection. Bigger from them submits a food to the returnable pump; through the smaller relay passes management of electromagnetic valves.

Sensors of frequency of rotation

Frequency of rotation of each separate wheel the sensor of frequency of rotation (defines all of their four pieces) and hands over this information to the control unit. For its part the control unit gives team to the hydraulic block.
Sensors of frequency of rotation consist of the magnetic core and the coil and are established at small distance from a gear washer – a rotor. A rotor, – as it is already clear according to the name, – rotates together with a wheel, why gear cambers on its perimeter depending on speed pass near the sensor quicker or more slowly. Each tooth running under the sensor, causes in it short-term increase in tension. Thus, in the sensor the electric impulse changing the frequency according to frequency of rotation is created. The signal arising thus is processed in the control unit as information on frequency of rotation. Rotors are located ahead on external hinges of leading semi-axes and behind on naves of wheels.

Electronic control unit

In the Sedan the control unit is located anti-blocking system (shooter) at the left under a back seat. In the versatile person this control unit is placed under the left lateral covering of a luggage compartment.


Similar sensors of frequency of rotation (shooter) are located in the car equipped with anti-blocking system, on all four wheels.

The control unit is located at the left under back sitting and processes arriving signals from sensors of frequency of rotation. At the same time it operates the hydraulic block so that wheels were not blocked. Along with difficult processing of signals and logic following this element the control unit contains also the blocking scheme. With its help the device can check itself, distinguish external mistakes and supervise working tension. If malfunctions are established, ABS is disconnected, on the dashboard the control bulb lights up.

Relay

Three relays participate in work of ABS:

  • The relay of electromagnetic valves is located under a cover on the hydraulic block.
  • The relay of the returnable pump is also located under a cover on the hydraulic block.
  • The ABS step-by-step relays and the relay of protection against retension are assembled in the combined relay.

Main switch

The models which have been let out to 07.92 g.

By means of the main switch located on the panel of switches on the dashboard at cars, 92 g let out till July, it is possible to disconnect ABS in order that in extreme road conditions it was possible to reach some reduction of a brake way. So, for example, if on the road the shchebenka or ice is scattered is covered with snow, when braking in front of tires