Like all objects around us, paper has its own dimensions and dimensions....
Let's start with definitions. What is a tachometer in a car? This is a device that records the crankshaft speed in a car.
Of course, its use is not limited to vehicles. Determining the number of revolutions per minute is necessary when working with various mechanisms:
- airplane turbine
- ship propulsion shaft
- power station generators
- high precision milling and lathes
- drilling rigs
- electricity and water metering devices.
In addition, instruments for measuring rotation speed are used in research work.
Any tachometer consists of two parts:
- The rotation sensor takes readings from the shaft - the object of measurement
- The signaling device either sends a command to the control circuit of the mechanism, or simply displays data on a pointer device (digital display).
The principle of operation of the tachometer is quite simple
There are several types of design:
Pulse electrical circuit
A mark emitting any field is installed on the shaft whose frequency is being measured. Most often this is a small magnet.
A reading device – a sensor – is placed next to the shaft. Pulses corresponding to the shaft rotation speed are formed on it.
An electronic circuit receives signals and outputs them to a display device. Instead of a magnet-sensor pair, a photo and an LED are sometimes used.
Then a disk with a hole is installed on the shaft, and reading occurs using flashes of light.
Advantage of the scheme– perfect accuracy. In fact, this is a digital device that works without errors. In addition, this scheme does not take power away from the engine.
Disadvantage: Requires power supply. This excludes the use of the device in purely mechanical units.
Generator type electrical circuit
The mechanism shaft is connected to a compact generator. Depending on the rotation speed, the amount of voltage generated changes.
Readings are taken with a device operating on the principle of a voltmeter. Another name is a DC tachometer. The main advantage is that there is no need for a power source.
Induction tachometer
This is also a generator circuit, only this design uses an asynchronous type machine. The stator coils are energized and as the rotor rotates, excitation occurs and the voltage increases linearly. 
Such devices have a high error and are not energy independent. But readings (unlike a DC tachometer) are taken at low speeds.
In chapter Service, Maintenance, Tuning to the question Tachometer. Tell me, is it possible to check the functionality of the tachometer without a car? given by the author Alexey Pronin the best answer is usually the tachometer has three outputs: power, ground, input, having figured out which is which (sometimes labeled + and -), apply supply voltage, relative to the ground “-”, apply a positive polarity signal to the tachometer input with a swing of 5-9 volts with a frequency from 10 to 100 Hz, pulse shape - preferably a meander with a duty cycle of 2
You can, apply impulses to the input, you can even short circuit its input with a positive wire, the arrow should twitch.
The speedometer is turned with a drill, and the tachometer is checked with a piezoelectric generator (lighter), connect the power and that’s it. !
if from the classics, then apply power and jerk the control wire to “-”, the arrow should bow
Alexey Losenkov, thank you for the advice, it worked!
How to check the tachometer yourself? Methods, tips and tricks
How to check the tachometer, especially if it is electronic and has an LED screen? First of all, you need to know that when the engine runs for a long time, harmful vibration occurs, which can lead to various types of damage to the devices and systems of the car. The tachometer cannot always avoid this fate. Basically, this could be a broken display, which will need to be replaced if it malfunctions.
Visible causes of problems must be eliminated immediately. This may be damage to the insulation of the electrical wiring, disconnection of wires from the tips, and, as a result, loss of contact.
If the wires are severely damaged, they must be replaced in such a way that relapses do not occur. If the sensor that is responsible for the number of engine revolutions breaks down, the needle begins to jump in different directions. This is a fairly common problem and can be solved by simply replacing the tachometer.
Before connecting the tachometer to the engine, you need to select the same device that was installed before the breakdown, or a similar device that will be exactly suitable for the type of your engine.
Typically it is red. The tachometer input wire must be connected to the distributor or to the switch, which depends on what ignition system is installed on the car. Don’t forget to also connect a wire to the size switch so that the device is illuminated.
Advice from professionals on how to test the tachometer yourself for functionality at home
Every modern car must be equipped with a tachometer. This device is a device designed to measure crankshaft rotation speed. Like any other device, this device can fail over time. How to check the tachometer at home, and for what reasons it may fail - look for answers to these questions below.
Possible malfunctions: signs and causes
The only sign that can indicate a malfunction of this device is sudden jumps in the instrument needle or its position at the zero mark.
For what reasons can this happen:
- Mechanical damage to the screen. Of course, if the display is damaged, it will have to be replaced; there are no other options.
- Problems in the wiring, poor functionality of the contact group as a result of oxidation. Such a problem can lead to disruption of the source of signal transmission that comes from the power unit to the device.
- In addition, the reason may be damage to the insulation of high-voltage wires connected from the distributor to the spark plugs. Such problems can lead to a lack of contact. If the cable is severely damaged, it must be replaced.
- Failure of the crankshaft sensor. If this controller breaks down, the instrument needle will jump sharply in different directions. This reason is one of the most common. The only solution in this case is to completely replace the device.
- Using silicone high-voltage cables instead of conventional ones.
Photo gallery “Types of tachometers”
If the first symptoms of a breakdown appear in the operation of the tachometer, then first of all it is necessary to diagnose the condition of the electrical circuits. As stated above, the reason may lie in poor contact or its absence, as well as damage to the circuit. Therefore, you need to check the connection, as well as the integrity of the cables. If even minor defects are detected, such as traces of corrosion, minor damage or cracks, weak fixation, the problem must be corrected, for example, using electrical tape. More serious defects require wiring replacement.
As practice shows, most often our compatriots are faced with tachometer inoperability after replacing the standard ignition cables with silicone ones. The device begins to work incorrectly as a result of the fact that silicone high-voltage devices have a different resistance value. In particular, in this case the shape of the signal changes. This problem can be solved by reducing the resistor on the CP circuit. If we talk about digital devices, then one of the most common malfunctions is the failure of the display (the author of the video is the liudusa channel).
This problem can only be solved by replacing the screen.
How to check a device if its needle jumps:
- Pay attention to the control panel to see if the Check Engine indicator lights up on it. If the lamp does not appear, checking the system will not reveal the problem.
- Check the integrity of the wiring using the voltage diagnostic method on the positive and negative contacts. In addition, make sure that all connections are securely connected.
- In the event that other devices are not functioning correctly, it is imperative to also check the mass, since this point is often missed. If the weight is bad, the tachometer will also work intermittently.
- If no defects are found, then it is also necessary to diagnose the condition of the contacts on the switchgear, that is, the distributor. You should also check the capacitor on the cap as it may be broken.
- Since high-voltage circuits are one of the main causes of malfunctions, it is necessary to check their integrity. In addition, all circuits in the ignition system are tested.
- If you changed the tachometer or repaired it, calibrating the device may solve the problem. To make the adjustment, adjust the position of the steering wheel or the device itself, check the correctness and quality of the connections.
- When the needle drops sharply as the speed of the power unit increases, most likely the cause should be looked for in the switch. Apparently, it is out of order and needs to be replaced.
Video “Replacing the device with your own hands”
How to change the device with your own hands and avoid making mistakes - see the video below (author - Dima Dimov).
Ivan Ivanovich Baranov
Experience working at a service station:
View all answers
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A tachometer is used to measure engine speed of exclusively carburetor cars.
This is a device located on the front panel.
It cannot be called super important, but for a novice driver who does not yet “hear” the engine of his car, it helps to calculate the number of engine and crankshaft revolutions.
It also plays an aesthetic role.
Many car owners like to show off modern instruments on the control panel.
The VAZ 2106 has a four-stroke four-cylinder engine, and during 1 revolution of the ignition distributor rotor, the contacts of the breaker, the so-called distributor, open and close four times.
Connection diagram
1 – tachometer;
2 – ignition coil;
3 – ignition distributor:
How to connect
The tachometer TX-193 of the VAZ 2106 works on the principle of measuring the frequency of voltage pulses occurring in the primary circuit of the ignition system. In a four-stroke four-cylinder engine, during one revolution of the ignition distributor rotor, the breaker contacts open and close four times. That is, four voltage pulses are generated per revolution of the rotor (or two pulses per revolution of the crankshaft). Thus, the pulse repetition rate is directly dependent on the engine crankshaft rotation speed, which, in fact, is reflected in the instrument readings.
In order to figure out how to connect a tachometer to a VAZ 2106, you just need to find out the purpose of the connected wires:
The white wire is used to connect the device backlight;
The red (thick) wire is connected through a fuse to the ignition switch; it receives power when the ignition is on;
White wire with a black stripe - for connecting to ground in any convenient place;
Brown goes to the “K+” terminal of the ignition coil, signals from this wire control the tachometer readings;
The black wire connects to the relay for turning on the charging current indicator, which is located on the right side under the hood;
The gray wire with a black stripe contacts the oil pressure sensor located on the left side of the engine.
Doesn't work, reasons
First of all, you need to check whether the tachometer is connected to the ignition coil. The second reason: the plus and minus contacts in the battery may have been accidentally mixed up. A malfunction may occur if the ignition wires are silicone. In this case, you need to change the value of the resistor on the board.
If your car is fuel-injected, the circuit from the ignition module to the fifth contact of the gearbox, and then to the tachometer, may be broken.
The arrow twitches
1. Check the check light on the instrument panel, if your car model has one. If it does not light up, then most likely the diagnostics will not show an error.
2. Check the wiring, and check not only the voltage level on the “positive” and “negative” wires, but also the quality of the contacts. Also be sure to check for the presence of “mass”, this is often what is overlooked. Usually other consumers, in this case, begin to work incorrectly.
3. A common cause of jerking of the tachometer needle is poor contacts of the distributor or failure of the capacitor located on the distributor; it very often breaks through - this is the most common cause of tachometer failure.
4. Check the ignition system. Often, malfunctions in this circuit lead to malfunctions of the tachometer, especially to a twitching needle.
5. If malfunctions in the tachometer appeared after disassembling or replacing it, then it may be necessary to adjust it. First, check its position: is it positioned correctly. Secondly, check the zero position. You can adjust it with the toggle switch on the back of the panel.
6. If the needle twitches at high speeds, then this is the first sign of the “death” of the commutator.
Malfunctions
Blown fuse #2 (10A) - Check for short circuit and replace fuse
Tachometer faulty - Check tachometer
Damaged electrical wiring - Restore electrical wiring
A device such as a tachometer does not in any way affect the operation of the engine or the driving performance of the car, but without it, the dashboard of a modern car will be incomplete. In this article we will look at why it is needed, how it works, what malfunctions it has, and how to deal with them without the help of specialists.
Tachometer VAZ 2106
The first car from the Zhiguli family equipped with a tachometer was the VAZ 2103. Neither the “kopek” nor the “two” had such a device, but they drove and drive without it to this day without any problems. Why did the designers need to install it on the panel?
Purpose of the tachometer
The tachometer is used to measure the crankshaft speed. Essentially, it is a revolution counter, showing the number of revolutions to the driver by deflecting the scale needle to a certain angle. With its help, the person sitting behind the wheel sees in what mode the car’s power unit is operating, and also whether there is any excess load on it. Based on the information received, it is easier for the driver to select the correct gear. In addition, the tachometer is indispensable when adjusting the carburetor. It is its indicators that are taken into account when adjusting the idle speed and the quality of the fuel mixture.
What tachometer is installed on the VAZ 2106
“Sixes” were equipped with the same tachometer as “threes”. It was a TX-193 model. Precision, reliability and excellent sporty design have made it a kind of standard automotive device. It is not surprising that today many car owners install these tachometers as additional devices. Moreover, they are equipped with motorcycle and even boat engines. As for the Zhiguli, the device can be installed without modifications on such VAZ models as 2103, 21032, 2121.
Table: main technical characteristics of the TX-193 tachometer
TX-193 is still on sale today. The cost of a new device, depending on the manufacturer, varies between 890–1200 rubles. A used tachometer of this model will cost half as much.
Design and principle of operation of the TX-193 tachometer
The “six” tachometer consists of:
- plastic cylindrical body with glass holder;
- a scale divided into zones of safe and dangerous modes;
- backlight lamps;
- a milliammeter with an arrow attached to its shaft;
- electronic printed circuit board.
The design of the TX-193 tachometer is electromechanical. The principle of its operation is based on measuring the number of electric current pulses in the primary (low-voltage) circuit of the car’s ignition system. In the VAZ 2106 engine, for one revolution of the distributor shaft, corresponding to two rotations of the crankshaft, the contacts in the breaker close and open exactly four times. These pulses are removed by the device from the final terminal of the primary winding of the ignition coil. Passing through the parts of the electronic board, their shape is converted from sinusoidal to rectangular, having a constant amplitude. From the board, the current flows to the winding of the milliammeter, where, depending on the pulse repetition rate, it increases or decreases. The arrow of the device reacts precisely to these changes. The greater the current, the more the arrow deviates to the right and vice versa.
Electrical diagram for connecting the tachometer VAZ 2106
Considering that the VAZ 2106 was produced with both carburetor and injection engines, the tachometer connection was different. Let's consider both options.
Connecting a tachometer in carburetor VAZ 2106
The electrical circuit of the speed counter of the carburetor “six” is quite simple. The device itself has three main connection wires:
There are also additional wires. They serve for:
- supplying voltage to the backlight (white);
- connections to the battery charge indicator relay (black);
- contact with the oil pressure sensor device (gray with a black stripe).
The wires can be connected either using a block or separately, depending on the year of manufacture of the device and its manufacturer.
In carburetor “sixes” with contactless ignition, the tachometer connection diagram is similar, except that the “K” terminal of the coil is connected not to the breaker, but to contact “1” of the switch.
Connecting a tachometer in injection VAZ 2106
In the VAZ 2106, equipped with engines with distributed injection, the connection diagram is slightly different. There is no breaker, no switch, no ignition coil. The device receives fully processed data from the electronic engine control unit (ECU). The latter, in turn, reads information about the number of crankshaft revolutions from a special sensor. Here the tachometer is connected to the power circuit through the ignition switch, the vehicle ground, the computer and the crankshaft position sensor.
Tachometer malfunctions
Despite the fact that the TX-193 tachometer is considered quite reliable, it also has malfunctions. Their signs are:
- lack of response of the needle to changes in engine speed;
- chaotic movement of the arrow up and down, regardless of the engine operating mode;
- obvious underestimation or overestimation of readings.
Find out the reasons for the VAZ 2106 engine malfunction:
What kind of breakdowns do the listed signs indicate?
The arrow does not respond to measuring the number of revolutions
Usually, the lack of response from the arrow is due to a broken contact in the connectors of the main wires of its connection, or damage to the wiring of the circuit. The first step is:
- Inspect the fastening of the conductor in brown insulation to terminal “K” on the ignition coil. If you detect poor contact, traces of oxidation, burning of a wire or terminal, fix the problem by cleaning the problem areas, treating them with anti-corrosion liquid, and tightening the fastening nut.
- Check the reliability of the connection of the black and white wire to the vehicle ground. If contact is broken, clean the wire and the surface to which it is attached.
- Using a tester, determine whether voltage is supplied to the red wire when the ignition is on. If there is no voltage, check the serviceability of fuse F-9, which is responsible for the integrity of the instrument panel circuit, as well as the condition of the ignition switch contacts.
- Disassemble the instrument panel and check the connections of the contacts in the tachometer wiring harness block. “Ring” all the wires going to the device with a tester.
Video: tachometer needle does not respond to engine speed
The tachometer needle jumps chaotically
Jumps in the TX-193 needle in most cases are also a symptom of malfunctions associated with its electrical circuit. The reasons for this behavior of the device may be:
- lack of good contact at the negative terminal of the battery;
- oxidation or burning of the brown wire on the ignition coil;
- burning or wear of the contacts of the ignition distributor cap or slider;
- wear of the distributor shaft bearing;
- shorting the red wire powering the device to vehicle ground;
- malfunction of the crankshaft position sensor (for injection engines).
A similar problem is solved by stripping the contacts, replacing the ignition distributor cap, slider, support bearing, restoring the integrity of the insulation of the device’s supply wire, and replacing the crankshaft sensor.
Video: tachometer needle jumps
The tachometer underestimates or overestimates the readings
If the device is outright lying, then the problem most likely lies in the ignition system. In other words, it shows correctly, but the number of pulses created by the chopper per revolution of the distributor shaft is more or less than four. If the tachometer readings are incorrect, there is usually a deterioration in engine performance. In this case, the speed may fluctuate, misfires periodically appear, which is accompanied by engine vibration and white or bluish exhaust.
In this case, the fault should be looked for in the breaker, or rather, in its contact group or capacitor. To fix this problem you need to:
- Disassemble the ignition distributor.
- Check the condition of the breaker contacts.
- Clean contacts.
- Adjust the gaps between the contacts.
- Check the serviceability of the capacitor installed in the breaker.
- Check the serviceability of the crankshaft position sensor. In case of malfunction, replace it.
However, the reason may be in the tachometer itself. Malfunctions occur related to the parts of the electronic board, as well as to the milliammeter winding. You can't do without knowledge of electronics here.
Incompatibility of the TX-193 tachometer with a contactless ignition system
Older models of TX-193 devices are designed exclusively for contact ignition systems. All owners of “sixes” who independently converted their cars to , then encountered problems with the tachometer. It's all about the different forms of electrical impulses arriving at the device from the breaker (in a contact system) and the switch (in a contactless system). The simplest way to solve this problem is to install a capacitor in the cut of the same brown wire coming from the breaker. But here it is necessary to experimentally select the desired container. Otherwise, the tachometer will lie. So, if you have no desire to engage in such experiments, just buy a device for a contactless ignition system.
Video: solving the problem of incompatibility of TX-193 with a contactless ignition system
Checking the correct operation of the tachometer
In a car service center, the accuracy of the tachometer readings is checked on a special stand that simulates the ignition system. The design of the stand includes a power source, a distributor and a counter of its shaft revolutions. The table below shows the calculated values of the distributor rotor speed and the corresponding tachometer readings.
Table: Calculated data for checking the tachometer
You can independently check how much the device is lying by connecting to it in parallel an autotester, the functionality of which includes a tachometer. It is necessary to turn it on in the desired mode, connect the positive probe to terminal “K” on the ignition coil, and the second to the “ground” of the car. Next, we look at the readings of both instruments and draw conclusions. Instead of an autotester, you can use a known-good tachometer TX-193. It is also connected in parallel to the one being tested.
Tachometer sensor
Separately, it is worth considering such an element of the tachometer circuit as its sensor, or rather, the crankshaft position sensor (CPS). This device serves not only to count crankshaft revolutions, but also to determine its position at a certain moment, which is necessary for the electronic control unit to ensure proper operation of the power unit.
What is a crankshaft position sensor?
DPKV is an electromagnetic device whose operating principle is based on the phenomenon of induction. When a metal object passes near the sensor core, an electrical impulse is generated in it, which is transmitted to the electronic engine control unit. The role of such an object in the power unit of the “six” is played by the crankshaft gear. It is to its teeth that the sensor reacts.
Where is the crankshaft position sensor located?
The DPKV on the VAZ 2106 is fixed in a hole on a special boss of the camshaft drive cover in the lower part of the engine next to the crankshaft gear. The wiring harness going to it can help determine its location. The sensor itself is enclosed in a black plastic case. It is attached to the timing cover with one screw.
How to check DPKV for performance
In order to determine whether the sensor is working, there are two methods. For this we need:
- wrench 10;
- screwdriver with Phillips bit;
- multimeter
The verification process consists of the following steps:
- Using a 10mm wrench, loosen the negative terminal on the battery. Let's take it off.
- Raise the hood and find the crankshaft position sensor.
- Disconnect the connector from it.
- Using a screwdriver, unscrew the screw securing the device.
- We remove the sensor.
- Turn on the multimeter in voltmeter mode with a measurement limit of 0–10 V.
- We connect its probes to the sensor terminals.
- With an energetic movement, we bring the blade of a screwdriver near the end end of the device. At this moment, a voltage jump of up to 0.5 V should be observed on the device screen.
- Switch the multimeter to ohmmeter mode with a measurement limit of 0–2 KOhm.
- We connect the probes of the device to the sensor terminals.
- The resistance of the sensor winding should be in the range of 500–750 Ohms.
If the device readings differ from those indicated, the sensor is faulty and must be replaced. The device is replaced in accordance with paragraphs. 1–5 of the above instructions, only in reverse order.
Replacing the tachometer VAZ 2106
If a malfunction is detected in the tachometer itself, it is hardly worth trying to repair it yourself. Even if he earns money, it is not a fact that his testimony will be correct. It is much easier to buy and install a new device. To replace the VAZ 2106 tachometer you will need:
- flat blade screwdriver;
- pliers;
- pencil, felt-tip pen or marker.
To replace the tachometer, you must:
- Remove the instrument panel trim by prying it off with a screwdriver.
- Move the panel to the side.
- Disconnect the wiring harness block from the device, as well as the connectors of additional wires, having previously marked their location with a marker or pencil.
- Using your hands or using pliers, unscrew the nuts securing the tachometer to the panel.
- Remove the device from the cover.
- Install a new tachometer and secure it with nuts.
- Connect and install the panel in reverse order.
As you can see, the tachometer is not such a sophisticated device. There is nothing complicated either in its design or in the connection diagram. So, if problems arise with it, you can easily deal with them without outside help.
Not many drivers know how to check the tachometer - one of the most important instruments in a car, which allows you to measure the number of engine revolutions. With its help, the driver can maintain full control over the operation of the engine so that the speed does not exceed the permissible values, and the engine does not fail in the future, since its repair will cost car owners a pretty penny.
If the tachometer suddenly fails and its needle either lies or does not show any values at all, then this problem must be solved as soon as possible. Naturally, first you need to find out the reason why it stopped working.
Causes of malfunction
How to check the tachometer, especially if it is electronic and has an LED screen? First of all, you need to know that when the engine runs for a long time, harmful vibration occurs, which can lead to various types of damage to the devices and systems of the car. The tachometer cannot always avoid this fate. Basically, this could be a broken display, which will need to be replaced if it malfunctions.
One of the problems may be electrical wiring problems and deterioration of the contact group due to oxidation. This may lead to the source of transmission of operating pulses coming from the motor to the tachometer being disrupted.
Visible causes of problems must be eliminated immediately. This may be damage to the insulation of the electrical wiring, disconnection of wires from the tips, and, as a result, loss of contact.
If the wires are severely damaged, they must be replaced in such a way that relapses do not occur. If the sensor that is responsible for the number of engine revolutions breaks down, the needle begins to jump in different directions. This is a fairly common problem and can be solved by simply replacing the tachometer.
We looked at the most common reasons tachometer failure. Eliminating such problems allows you to restore normal operation of the tachometer. If checking the tachometer was unsuccessful and the diagnostics did not bring any results, then you need to seek help from specialists at a service station.
How to replace a faulty tachometer yourself?
Before connecting the tachometer to the engine, you need to select the same device that was installed before the breakdown, or a similar device that will be exactly suitable for the type of your engine.
Look at the wires of the old device: one black wire comes from it, which is negative, and it must be connected to the car body. The positive wire should be connected directly to the ignition switch.
Typically it is red. The tachometer input wire must be connected to the distributor or to the switch, which depends on what ignition system is installed on the car. Don’t forget to also connect a wire to the size switch so that the device is illuminated.
If you don’t know how to check the tachometer and find out how accurately it works, then you can install a digital analogue in your car, which has a higher accuracy class. A proven pointer gauge when driving at speed is visually perceived much better than a digital tachometer.
