Control instrument sensors (VAZ-2101)

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Coolant Temperature Gauge Sensor

On Zhiguli cars, a TM-106 type sensor is used, which is screwed into the cylinder head on the left side of the engine.

A thermistor 2 is installed in the bronze body 1 of the sensor, changing its electrical resistance depending on the temperature. The thermistor is pressed against the body and one side of it is connected to ground through the body. The other side is connected to the plug through the cup 3 and the spring 4. The plastic holder 6 of the plug is crimped in the body. The spring, the spring cup and the side surface of the thermistor are insulated from the walls of the body by a paper cartridge 5.

Oil pressure indicator sensor

The sensor is used on VAZ-2103 cars and works together with the UK-194 oil pressure indicator located on the instrument panel. Sensor type MM3-93A. It is installed on the engine cylinder block on the left side.

The sensor converts the pressure in the engine lubrication system into the resistance of the electric circuit. It has a diaphragm 14 made of beryllium bronze, which bends under pressure and moves the brushes of the variable resistor 8 through a lever mechanism, changing the electrical resistance of the sensor.

The sensor body is stamped bronze. For self-cleaning of the hole in the body for the passage of oil, a wire rod 15 is inserted into it. The diaphragm is rolled onto the body. A pusher 16 is soldered in the center of the diaphragm. The body with the membrane is pulled together with the cover by a steel rim. A variable wire resistor and a mechanism for driving its brushes are fixed on the cover. From the outside, the sensor is covered with a steel casing rolled onto the body.


Resistor 8 is wound with nichrome wire on a glass-textolite plate. The beginning of the winding is fixed on the plate, and the end is connected to a plug mounted on casing 7 in a plastic holder. The brushes are connected to ground.

When pressure acts on the diaphragm 14, it bends, the pusher 16 presses on the intermediate lever, and that, in turn, on the brush lever and, overcoming the tension of the return spring 10, turns the brush lever relative to the axis. The brushes move from the beginning of the resistor winding to the end. When the pressure decreases, the deformation of the diaphragm decreases and the return spring pulls the brush lever, returning the brushes to the beginning of the winding.

Low Oil Pressure Warning Light Sensor

On Zhiguli cars, the MM-120 type sensor is used in the circuit for signaling emergency low oil pressure in the engine lubrication system. It turns on a control lamp with a red light filter in the instrument cluster (on VAZ-2101 and VAZ-2102) or in the oil pressure gauge (on VAZ-2103), if the oil pressure is below normal. The sensor is screwed into the engine cylinder block on the left side.

In the steel housing 1 of the sensor, a diaphragm 14 made of polyester film and a fixed contact 19 with a plastic pusher 16 are rolled. A plastic insulating cap 21 is installed and rolled in the housing. A movable contact 20 is pressed against the fixed contact by a spring. The fixed contact is connected to ground through the housing, and the movable contact is connected to the plug through a spring and a contact sleeve 23. In the contact sleeve there is an opening closed by a filter plug 22, through which the above-diaphragm cavity of the sensor communicates with the atmosphere.

If the pressure in the engine lubrication system is below 0.4-0.8 kgf/cm² (0.2-0.6 kgf/cm² since 1976), the moving contact is pressed by a spring to the fixed contact, the control lamp power supply circuit is closed and the lamp lights. As soon as the oil pressure exceeds 0.4-0.8 (0.2-0.6) kgf/cm², the diaphragm bends and, overcoming the resistance of the spring, the pusher presses the moving contact away from the fixed contact. The control lamp power supply circuit is opened and the lamp goes out.

Handbrake indicator lamp relay-interrupter

The relay-interrupter is designed to obtain intermittent burning of the handbrake control lamp. The relay-interrupter type is RS-492. It is suspended on wires under the instrument panel behind the fuse box.

The relay-breaker has a plastic base 36, in which three posts-plugs 35, 38, 39 are fixed, designated "+", "L" and "—". A bimetallic plate 37 with a winding of nichrome wire, insulated from the plate with asbestos paper, is welded to the post-plug "I". The resistance of the winding is 26 Ohm at 20°C. One end of it is welded to the post-plug "—", and the other to the contact riveted to the end of the bimetallic plate. The relay-breaker is covered from above with an aluminum stamped casing 7.

When the bimetallic plate is cold, it is pressed against the "+" plug and the contact of the plate is closed with the contact of this plug. When the contacts of switch 54 are closed, the current flows along the path: power sources - plugs "30/1" and "15" of the ignition switch - plugs "10", "9", "I" fuse box, and then splits into two circuits. One is closed to ground along the path: plug "+" of flasher relay 49 - handbrake control lamp 43 - plug "L", bimetallic plate 37 and through the closed contacts of flasher relay 55 to plug "+" - switch 54 - ground. In this case, lamp 43 is on. The other circuit is closed to ground along the path: plug "I" of fuse box 53 - plug "-", winding of flasher relay 55 and through its closed contacts to plug "+" - switch 54 - "ground". The current flowing through the winding of flasher relay 55 heats it. Bimetallic plate 37 bends from heating and the contacts of the flasher relay open. The current in both circuits stops and lamp 43 goes out. Bimetallic plate 37 cools down and takes its previous shape. The contacts of the relay-breaker close again, turning on the control lamp, and the described cycle is repeated with a frequency of 60-120 times per minute, causing the handbrake control lamp to flash.

Fuel level indicator sensor

To control the fuel level in the tank, VAZ-2101 and VAZ-2103 cars use sensors of the BM-150 type, and VAZ-2102 cars use sensors of the BM-154 type. They have the same design and operating principle and differ only in the size and shape of the float lever and the receiving tube. The sensors are used together with fuel level indicators of the UB-191 or UB-193 type. The sensor flange is attached to the fuel tank with six screws.

A receiving tube 27 with a mesh filter 34, through which fuel is sucked from the tank, is welded to the flange 29. A plastic housing is mounted on a support plate 31 welded to the tube. A resistor 32, wound with nichrome wire on a plastic plate, and a fixed contact 26 for switching on the fuel reserve indicator lamp are riveted to the housing. Two plugs are mounted on the flange, designated "W" and "T". Plug "W" is connected to fixed contact 26 by plate 28, and plug "T" is connected to the lower end of the resistor winding by plate 30. A hollow plastic float 24 is fixed to the long end of lever 25, and contact spring 33 is fixed to the short end, connected to ground through lever, tube 27, flange 29 and a special wire, the tip of which is clamped by one of the flange fastening screws. One of the petals of spring 33 slides along the resistor winding depending on the fuel level, including a greater or lesser number of resistor turns in the level indicator circuit. The other petal, when the float is in the lower position, closes with contact 26, including the fuel reserve control lamp.

Handbrake indicator light switch

The switch type VK-409 is installed on a special bracket under the handbrake lever. On VAZ-2103 cars, the same switch is also used to turn on the control lamp of the carburetor air damper. This switch is installed under the instrument panel next to the air damper control handle.

In the housing 1 of the switch, the rod 41 moves, at the end of which a movable contact 40 is fixed on a plastic insulating sleeve. This contact is pressed by a spring against the housing connected to the ground. When the brake lever is released (brake off), he presses on rod 41 and moves contact 40 away from the housing, opening the circuit of control lamp 43.