Audi 80/Avant (B4)

Since 1991-1995 of release

Repair and car operation

The hydraulic block

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 block of management pressure in brake system is supported to constants, decreases or created again. However this pressure cannot be above that is created in the main brake cylinder after pressing of a pedal of a brake by the driver. Pressure regulation is carried out by four quickly включающимимся valves 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, simply to leave in a receiver (differently thereof the brake pedal simply would fail), the powerful returnable pump pumps over a 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 enters ABS. If to listen, it is possible to hear and pump noise. The noise isolation in the hydraulic block slightly muffles sounds of work of the pump.

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

Gauges of frequency of rotation

Frequency of rotation of each separate wheel the gauge of frequency of rotation (defines all their four pieces) and hands over this information to the management block. From its part the management block gives a command to the hydraulic block.
Gauges of frequency of rotation consist of the magnetic core and the coil and are established on small distance from a gear washer – a rotor. A rotor, – as it is already clear under the name, – rotates together with a wheel, paternal gear cambers on its perimetre depending on speed pass near to the gauge faster or more slowly. Each tooth running under the gauge, causes in it short-term increase in pressure. Thus, in the gauge the electric impulse changing the frequency according to frequency of rotation is created. The signal arising thus is processed in the management block as the information on frequency of rotation. Rotors are located ahead on external hinges of leading semiaxes and behind on naves of wheels.

The electronic block of management

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

The relay

Three relays participate in work ABS:

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

The main switch

The models which have been let out till 07.92

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