Audi A4

since 1994 of release

Repair and car operation



A4 Audi
+ Running gear
+ Regular servicing
+ Engines
+ Turbo-supercharging
+ exhaust System
+ cooling System
+ Fuel tank and fuel pump
+ Air filter and absorption channels
+ injection System
+ Coupling
+ Transmission and main transfer
+ Suspension bracket of wheels and steering
+ Brakes
+ Wheels and tires
+ Electrotechnical equipment
- Ignition system
   That provides ignition
   When there is an ignition of a fuel and air mix?
   Different systems of ignition
   So there is an ignition spark
   Executive body
   System brain
   The signals arriving in the control unit
   Detonation adjustment
   Be careful in the address with ignition
   Works on ignition system
   Search of malfunctions in ignition
   Ignition distributor
   Knot of a high voltage
   Replacement of spark plugs
   Right choice of spark plugs
   Check of the moment of ignition
+ Lighting
+ Alarm equipment
+ Tools and devices
+ Heating and ventilation
+ body Details
+ Salon
Search of malfunctions
Technical characteristics





The signals arriving in the control unit

Hall sensor

The disassembled sensor of the Hall of the engine with working volume of 1,8 l. The major details are integrated system of the Hall (in the case with the socket) and a diafragmenny rotor.

Very much simply it is possible to tell: the sensor of the Hall provides inclusion and current switching off to the ignition coil (a bypass way via the control unit and the terminal cascade). It is called in honor of an opener of effect of the Hall who is used in this sensor.

The sensor of the Hall consists of the following details: from a diafragmenny rotor, for example, with four dredging (depending on number of cylinders), a constant magnet and the direct integrated system of the Hall located opposite to it. All this works as a light lock, only here instead of light work with electromagnetic radiation.

If the diaphragm of a rotor is in an electromagnetic field, the sensor of the Hall starts up a current to the control unit. When the diaphragm leaves from an air gap between integrated system of the Hall and a constant magnet, the current does not arrive in the control unit. These are signals for ignition. The sensor of the Hall settles down:

  • in the engine in capacity of 74 kW under the distributor;
  • in the engine in capacity of 92 kW and in the four-cylinder engine in capacity of 110 kW ahead at the left on a head of the block of cylinders;
  • in the six-cylinder engine behind on the left head of the block of cylinders.

Sensor of number of turns and sensor of the moment of ignition

In addition to the Hall sensor information in the control unit arrives from the sensor of number of turns of the engine and the sensor of the moment of ignition (the last only in the six-cylinder engine). Both are so-called induction sensors.

The sensor of number of turns of the engine functions as follows: in the sensor the coil and a magnet are placed. The interfaced detail is formed by gear heights on a gear wreath of a flywheel behind on the crankshaft. Each time when the tooth passes under the sensor, changes a magnetic field of a constant magnet, and in the coil there is a tension. In the form of tension it is enough this small signal for the subsequent processing in the control unit. Available also information on frequency of rotation of the crankshaft.

To define exact position of the crankshaft, in a certain place on perimeter of a flywheel the steel pin was placed. When the pin passes under the sensor, there is a tension peak that is used by the control unit for definition of position of the crankshaft.