Audi A4

since 1994 release

Repair and operation of the car

Speedometer in Audi A4, differently also could not be, is the electronic measuring device as well as the measuring instrument of number of turns. It also processes impulses of number of turns which he (not as a tachometer) receives from the sensor on a transmission. There it is measured, with what frequency wheels rotate.

The signal of rotation of wheels is used as measuring size for run definition, and also in operation of the indicator of an interval of maintenance, the fuel consumption indicator, in volume control of a sound of the radio receiver and in operation of the on-board computer. Therefore there was an idea to send this signal and to a speedometer and to refuse a shaft of a speedometer which provides the drive in old mechanical speedometers.

If the speedometer does not work, in the beginning check the corresponding safety lock in a box of safety locks (the head the Electrotechnical equipment).

Run counter

Indication of the general and day run in Audi A4 is carried out by the liquid crystal display. That it was impossible to manipulate data on run – data on run continuously remain in the memory independent of giving of tension and the combined device which is in.

Pulse sensor of a speedometer

Impulses of rotation of wheels move in a speedometer the sensor with gerkonovy contact behind on a transmission. Gerkonovy contact represents the block of contacts which are placed in an air-tight gas cover. Contact becomes isolated in case it is influenced by an electromagnetic field.

In order that gerkonovy contact could give out sequence of impulses, it has to open and be closed in beat frequencies of rotation of wheels. Therefore the wheel with dredging which rotates in front of the sensor, influences the magnetic field influencing the block of contacts.

Check of the pulse sensor of a speedometer

Dismantle of the pulse sensor of a speedometer