The cars are equipped with a speedometer, a combination of instruments, a two-pointer pressure indicator, blocks of control and signal lamps, signaling devices indicating to the driver an extreme state in a particular system, a set of sensors, switches and switches.

The instrument cluster (Fig. 1) includes indicators: fuel level, coolant temperature, engine oil pressure, voltage (voltmeter).

In addition, the combination includes signaling devices for overheating of the coolant, low (emergency) oil pressure in the engine and fuel reserve.

The connection diagram of the instrument cluster with sensors is shown in fig. 2.

Each combination device consists of a plastic block 5 (see Fig.1), which carries the windings W1, W2, W3,

Between the windings there is an axis on which a permanent magnet and an arrow of the device are mounted. A permanent magnet 6 is pressed into one corner of the shoe.

In the absence of current in the circuit, the fields of these two magnets interact and place the arrow in the leftmost position.

When the current is turned on, the latter passes in series the windings W2 and W3 and the temperature compensation resistance RTK, which serves to stabilize the readings of the device when its temperature changes.

At the same time, the current passes through the winding W1 and the resistance R of the sensor.

The resistance of the sensor changes: for the oil pressure and fuel level sensor by changing the position of the rheostat slider, for the temperature indicator sensor by changing the resistance of the thermistor itself.

When the resistance of the sensor changes, the current in the winding W1 changes. Since the current does not change its value in the windings and W3, the position of the arrow of the device depends on the interaction of the fields and windings W2 and W3 with the winding field W1, which changes its value.

The resulting field of all coils sets the disk magnet of the arrow to the appropriate position.

Two pressure gauges installed in the UK168 gauge and showing air pressure in the brake system circuits work in a similar way.

The speedometer, made in the same style as the instrument cluster, works in conjunction with a sensor mounted on the gearbox (Fig. 3).

A three-way worm wheel 3 is mounted on the secondary shaft of the gearbox, which engages with a driven worm wheel 4, made integral with the roller.

A spur gear 1 is mounted on the shaft shank, which meshes with gear 5 of the speedometer sensor drive.


Maintenance of control and measuring devices is reduced to maintaining the devices and sensors in good condition, for which it is necessary to wipe the instrument scales and the sockets of the blocks of control and signal lamps with a dry rag weekly, and also monitor the reliability of the fit of the protective rubber covers on the sensor housings.< /p>

Incorrect fit of the covers can lead to failure of the plug connection due to moisture and dirt.

After every 30 thousand km of run at the next TO-2, it is necessary to remove the grease from gears 2 of the cylindrical cavity and 5 of the speedometer (see Fig. 3) and replace it with a new one. To lubricate gears, CIATIM-201 grease is used.

Possible malfunctions of devices and ways to eliminate them

- Cause of malfunction


Fuel, oil pressure and temperature gauges do not work

Voltage indicator works

Fuse #8 blown

Replace fuse

Voltage indicator does not work

Fuse #6 blown

Replace fuse

Control or signal lamps in blocks do not light up

Fuse #8 blown

Replace fuse

The corresponding lamps in the block burned out

replace lamps

The current-carrying track on the block board has burned out

Inspect and fix block

Understated or overestimated instrument readings (pressure gauges, temperature gaugess and fuel)

The corresponding sensor is faulty

Replace sensor

Device is defective

Replace instrument

The coolant overheat, fuel reserve, or low oil pressure warning lights are off

The corresponding sensor has failed

Replace sensor

Appliance repair

If the devices fail, first of all, determine the serviceability of fuses No. 6 and 8. After making sure that the fuses are in good condition, you can search for the malfunction that has occurred.

The simplest method for diagnosing faults in a system of instrumentation is to sequentially replace sensors first, then pointers.

Before such a check, it is necessary to make sure that the circuits from the devices to the sensors are in good condition. To do this, disconnect the wire from the sensors and close it to ground.

In this case, the arrows of the temperature and pressure indicators should take the extreme right position on the scale.

When disconnecting the wires from the ground, the arrows should return to their original position.

The deviation of the arrow and its return to its original position indicate the health of the electrical circuit from the device to the sensor.

The arrow of the fuel level indicator should be set to the zero mark of the scale when the wire at the sensor is shorted to ground.

If the instrument circuits are OK, then the corresponding sensor is replaced.

If after this the device does not work normally, it should be replaced.

Instruments and sensors cannot be repaired, and in case of failure they are completely replaced.

If necessary, assess the accuracy of instrument readings should be guided by the following data.

The voltage indicator has colored zones, on the red zone there is a strip corresponding to a voltage of 24 V, on the green zone - 28 V.

Pressure, fuel level and temperature gauges are checked against the control resistance according to the scheme shown in Fig. 4.

The devices are connected to a 24 - 26 V DC voltage source and to a resistance box.

For this purpose, you can use the MKS-6 resistance store or any other that allows you to gain resistance from 50 to 560 ohms at intervals of 0.5 ohms.

The wires I, II and III from the devices of the combinations are connected in turn to the resistance box, and the resistances indicated in Table 1 are collected on the store.

The fuel gauge sensor has built-in contacts for the fuel reserve indicator.

In case of failure of the signaling device, the orange wire of the plug-in block of the sensor installed in the tank should be shorted to ground.

At the same time, if the circuit is working, the signal lamp installed in the instrument cluster should light up. If the lamp does not light up, the sensor is defective and must be replaced.

If the speedometer fails, first remove the sensor from the car and check it according to the scheme shown in fig. 5.

Using a test lamp 5, the correctness of the sensor windings is checked by connecting the voltage in turn to terminals 1 - 2; 2 - 3 and 1 - 3 sensor connectors.

In this case, the control lamp should be on, which indicates that the sensor windings are working.

If in one of these measurements the lamp does not light up, the sensor is faulty and must be replaced. After checking the integrity of the windings, the sensor is checked for a short circuit to the case.

Checking is done with a test lamp. In this case, the lamp should not burn, which indicates that the sensor is working. If the speedometer does not work with a good sensor, the pointer should be replaced.