Everyone knows that a tachometer is included in almost every dashboard in modern vehicles. However, not all drivers know exactly why this device is needed. In this article we will tell you what, in fact, a tachometer is, what they are, and we will analyze the main causes of its technical malfunctions.
A tachometer is a device that measures and shows in real time the number of revolutions of the crankshaft of the power apparatus. It can monitor changes in engine speed to avoid too low or, conversely, high crankshaft speeds.
In the process of driving a car or other vehicle, the device helps the driver to upshift in a timely manner, based on his testimony. Even the most inexperienced motorist will be able to change speed in time when the arrow of this device approaches the red zone or, conversely, drops down to the minimum. Also, it is worth saying that with the help of a tachometer, the desired mode of operation of the engine is selected.
Tachometers are both digital and analog, they can reset the received data, and the accuracy of their readings is rather arbitrary and can change.
Digital tachometers have an electronic display that displays all the necessary information about the speed of the power unit. Such devices are used to set up and adjust the operation of the economizer, electronic ignition, as well as the entire engine.
The analog tachometer is more popular and used more often than the digital one. And all because of the ease of use. When driving, special accuracy is not required, the speed is shown by an arrow moving along a calibrated dial. If the operation of the sensors is incorrect, then the arrow twitches and it becomes impossible to control the speed. The design of this device has been created and changed over the years, so using it is simple and reliable.
If, when starting the engine and while driving the vehicle, the tachometer needle jumps or points to the zero mark, this means that the device is out of order. There may be several reasons for this. However, most often, the cause of the breakdown is the replacement of high-voltage ignition wires. Poor wiring condition can also cause the tachometer to malfunction.
Malfunction in the operation of the tachometer
If signs of a malfunction appear, for starters, you should pay attention to the general condition of the wiring. Very often, damage to the wires or lack of contact in them can cause a breakdown of the tachometer. Various minor defects, in the form of traces of corrosion, minor cracks or loose fastenings, are easy to eliminate, but if the damage is serious, the wiring will need to be replaced.
An equally relevant cause of failure is the installation of silicone ignition wires instead of regular ones. This is because the per unit resistance of silicone wires is very different from the resistance of the factory wires. As a result, the shape of the current pulse changes. If you reduce the value of the resistor on the KP board, then the malfunction is eliminated by itself.
With regard to digital tachometers, a common cause of device failure is often a breakdown of a special digital screen that shows the current parameters of the car. To resume the operation of the device, you will have to change the LED display.
It is also not necessary to exclude the breakdown of other parts; it is necessary to identify which element is broken and replace it with a new one.
Why does the tachometer needle jump
To find out why the tachometer needle is twitching, it is necessary to perform the following manipulations:
1. On the dashboard, find the “Check” lamp and check if it lights up. If not, then, most likely, the system diagnostics will not be able to determine the malfunction.
2. Perform a wiring test by testing the voltage level on the plus and minus wires, and check the condition of the connections.
3. If other equipment or instruments do not work correctly, it is imperative to check the mass, because this detail is often overlooked.
4. Check the condition of the contacts of the distributor and the capacitor on its cover, as it could be broken during operation.
5. Also, you need to check the circuits in the ignition system.
6. If you have recently repaired the device or replaced it, then it just needs to be configured. To do this, you need to adjust the zero position and the device itself, adjust the connection quality and adjust the toggle switch on the back of the unit.
7. If the arrow jumps when the engine reaches high speeds, then the switch is broken and needs to be replaced.
Buy a tachometer for a car
The digital tachometer looks like a scoreboard with luminous numbers that show the frequency of movement of the motor parts.
It is useful when performing ignition electronics tuning operations, setting the fuel saturation state, when the engine is running at full power, or when gradual acceleration is required. It is considered the most accurate and, most often, is chosen, if necessary, to adjust the idle speed or check other devices similar to it.
As for the analog tachometer, they are presented as a dial with an arrow. Such a device is considered more modern, popular and convenient, since the dial is easier for drivers to perceive and allows you to analyze the situation much faster than in the case of numbers. Therefore, when choosing a tachometer, you need to decide which characteristics are preferable and more important for you. However, one way or another, the presence of this important sensor is very necessary on the road, if only because it will allow you to determine in time about the presence of various problems in the engine of your car.
Installing a new tachometer with your own hands, a phased progress of work
You can install a tachometer on any machine, this procedure is not complicated and does not require contacting a workshop. However, the installation process itself depends on which engine you have under the hood - diesel or gasoline. I propose to consider the methods of connecting the tachometer in more detail.
Installing a tachometer on a car with a gasoline engine
If your car is equipped with an ignition system, then you first need to mount the device itself. Very often, drivers operate a remote tachometer.
Directly the scheme of mounting the device looks like this:
1. The “minus” wiring, which often has black insulation, is connected to the vehicle ground.
2. The power wiring usually looks red and is connected to the appropriate ignition switch terminal.
3. If the car circuit is contact, then the wiring that is connected to the measuring input of the device is connected to the ignition coil terminal connected to the distributor breaker. When a non-contact circuit is used in the machine, the third wire is connected to the switch.
If the tachometer is equipped with a backlight, then it is connected to the dimensions of the machine using a special ignition switch terminal.
Installing a tachometer on a car with a diesel engine
1. When your car has a diesel engine, the test lead of the device must be connected to the generator terminal marked with the symbol "W".
2. If you cannot find it, you need to disassemble the generator and get to the wiring that connects the winding and the rectifier.
4. Ultimately, you need to assemble the generator back.
As you can see for yourself, tachometers are different, so it is very important, before buying such a device, to ask the seller if this unit will work correctly on your car.
Surprisingly, until quite recently there were no tachometers at all and the drivers somehow coped. However, modern motorists are used to the fact that everyone makes special settings for them. Rumor has it that the manufacturers of the Mazda car brand want to bury such a device as a tachometer and exclude it from the instrument panel.
Pulse frequency converter or electronic tachometer for a carburetor engine. In today's article, we will talk about devices that are designed to help drivers in driving, as well as timely notify about various indicators. As it is already clear, we will talk about a tachometer, this device has long been known to drivers and many are familiar with the principle of its operation.
Particularly popular device among riders, there is nothing to do without it. In racing cars, they are guided only by the readings of the tachometer, the speedometer does not play a role. Experienced drivers also willingly use this gadget, it helps correctly, in this way the load on the engine is minimized. About what types of motors can be installed and how to do it, consider a little lower.
Installation methods for different types of engines
Electronic tachometer for carburettor car engine VAZ or GAZ can only be summed up in one way, this is . If we were talking about mechanical, then I would advise you to bring the device to the speedometer cable to read the readings. In the meantime, we have an electronic version, then let's consider it.
So, ET is a small-sized modular unit consisting of a display and buttons.
When connected to the ignition system there is a process, familiar to us from physics, of converting an impulse into an electromagnetic field.
As a result the device will display indicators in the form of revolutions per minute and the charge from the generator. More sophisticated ETs can show a lot of related information, such as temperature outside and in the cabin, fuel consumption, speed, and other unnecessary and distracting notifications.
When mounted on a four-cylinder engine, one revolution will correspond to two units of impulse. The injection type provides for connection to an ECU (electronic control unit), which will transmit data on crankshaft speed. The diesel type also makes it possible to connect, but the method depends on the specific type.
- Electronic tachometer recommended for inexperienced drivers who can not navigate by the sounds of the engine;
- When purchasing, pay attention to the back of the package, where it is written for which car brands it can be used. Otherwise, the readings will not be true, or get ready for problems in the electrical circuit (this applies more to injectors);
- Install the module itself directly somewhere in a conspicuous place so that you can always see its readings without any problems. As practice shows, installation is carried out on the central panel of the torpedo. Some manage to sharpen the oblong module into the instrument panel in place of the "STOP" indicator, this is for models 2108, 2109, 21099 .
Wiring diagram for carburetor type
We start the red wiring from the ET to the plus of the ignition terminals, we ring the mass somewhere on the body, no difference, and the minus directly to the coil. Do not forget that at night we also need to read the readings, therefore, depending on the model, there is an additional wire that must be connected to the dimensions. During the inclusion of the latter, the display of our ET will light up.
If you do not want to take part in this process or you do not have enough experience, do not take risks, drive the car to a service center. Where qualified specialists will promptly and efficiently install the device for you, consult on how to use it safely and other points.
Every modern driver should have at least a general idea of how to connect a tachometer. Despite the fact that this device is not mandatory equipment, its use can significantly extend the life of the engine, avoiding costly repairs or premature replacement of the motor.
Benefits of using a tachometer
The tachometer continuously informs the driver about the speed of rotation of the crankshaft, thereby helping to find the optimal time to change gear. Also, the tachometer readings allow the motorist to fine-tune the carburetor and other important vehicle devices while the internal combustion engine is running with the car stationary.
Types of tachometers
Tachometers are divided into two types:
- Standard tachometers. Mounted in the dashboard of the machine at the factory. Most cars are equipped with this type of device.
- Remote tachometers. In the vast majority of cases, they serve as an alternative to the missing standard measuring device, and are less often used as a tuning element. Remote tachometers are installed directly on the dashboard of the vehicle.
How to install a tachometer yourself
The process of installing a tachometer on a car with a gasoline engine is different from installing this gauge on a car with a diesel engine. Based on this, the article will consider both installation methods.
Installation of a tachometer on a vehicle with a gasoline engine
If a tachometer connection diagram is attached to the device, it is strongly recommended to study it in detail and make the connection in accordance with the accompanying documentation. In the absence of a scheme, the installation of the device is carried out in several stages:
- The device, depending on the type, is fixed either in the appropriate seat on the dashboard or on its surface.
- The black wire is connected to the body (ground) of the vehicle.
- The red wire connects to the ignition switch terminal, which will supply 12 volts when the ignition system is on.
- The third wire of the device can be painted in any color. It must be connected taking into account which ignition system is installed on the car. If the system is contact, the tachometer must be connected to the distributor breaker. With a contactless ignition system, the device is connected to a voltage switch.
- To provide backlighting of the display, if provided by the manufacturer, the device should be connected to the terminal intended for this purpose on the ignition switch.
Installation of a tachometer on a vehicle with a diesel engine
The device should be connected to the generator, so the installation of the tachometer is best done on a viewing hole or overpass. Before starting work, the generator protection is dismantled. Next, on the generator, you need to find the terminal with the Latin letter “w” and connect the output wire of the tachometer to it.
At the next stage, the contact closes, which moves away from the oil pump. This action is performed in order for the tachometer to give reliable readings.
It should be noted that sometimes it is not possible to find a generator terminal with the Latin letter “w”. In this case, you need to disassemble the generator, connect one of the three wires that connect the winding and the rectifier to the tachometer cable and insulate the junction well. After that, the generator is assembled in the reverse order.
In conclusion, it should be noted that installing a tachometer is not a very difficult job, but it is strongly not recommended to start its implementation without theoretical knowledge and some practical experience related to car repair. Without firm confidence in your own abilities, it is best to leave the car at the disposal of qualified employees of a specialized station, who will be able to install a tachometer on your vehicle as soon as possible.
Video
Tachometer installation procedure from VAZ 2106 to VAZ 2105:
An electronic automobile tachometer is a control and measuring device that reflects information about the engine speed (rpm). The values of this indicator are used when adjusting the idle speed, choosing the moment of gear shifting and monitoring engine operating modes.
How does an electronic tachometer work?
Speeds read the number of revolutions of the crankshaft of the engine and create electrical impulses that are converted into numerical values in the tachometer. Unlike the traditional (analog) one, installed on many cars at the factory and using arrow indication, the electronic tachometer reflects the exact digital value of the crankshaft speed. The measurement error of the device does not exceed 100 rpm, while for analog samples this figure can reach 500 rpm.
Device
Automotive electronic tachometer consists of:
- digital scoreboard;
- microprocessor;
- microcircuits;
- control sensor on the idle valve;
- counter (converter).
As already mentioned, the instrument readings are displayed on the scoreboard. The device is powered from the car's on-board network with a voltage of 12 V, the value of the current consumed is up to 120 mA.
Another advantage that an automotive electronic tachometer has compared to an analog tachometer is the ability to combine various functions in one device:
Before installation
Some car models (especially small ones) are not equipped with a tachometer as standard, so the owners of such models more than others need to receive important and objective information about the operation of the engine. As a result, in retrofitting the car with an electronic tachometer. Car enthusiasts who are already accustomed to seeing a dial gauge on the dashboard can install an electronic car tachometer to get more accurate readings, implement additional functions or give the interior a more stylish look.
It is very important to consider that electronic tachometers are offered for engines with a different number of cylinders, which is indicated in its characteristics. If you use the device in a vehicle with an engine with a different number of cylinders, there is a risk of obtaining false data.
When purchasing a car electronic tachometer, you need to familiarize yourself with its technical characteristics, and also check with the seller whether it is possible to install it on a specific car, since the reading algorithms for gasoline and diesel engines are different. There are also universal devices.
How to install an electronic tachometer depends on its size and design. You can fix it on top of the "dashboard" using double-sided tape, a bracket, or install it in the panel in a free space, possibly instead of equipment (for example, clocks).
Models of electronic tachometers
Helios 148/360/361/500
They have a standard look. Designed for use on cars with carburetor engines, the number of cylinders is from 1 to 16. They are mounted on top of the instrument panel.
The advantages of this series are the low price, as well as the maximum a set of additional functions - almost all of the above, as well as a car parking timer and alarm simulation. The stated measurement error of devices is quite low: up to 5 rpm. The models of the line differ in the control scheme (one or two buttons), the number of display segments (3–5), and the ability to change the brightness of the indicator.
Multitronics
Multironics DD5/DM10/DM20 tachometers are less versatile. Of these, only the first model has a clock and a timer as additional functions, automatic adjustment of the display brightness, the rest have only a voltmeter. The measurement error is somewhat higher - at 2000 rpm it is 10 rpm, and at high speeds - up to 3%. DD5 also differs in that it can be used for a wide range of engines - with 2, 4, 5, 6 and 8 cylinders, both gasoline and diesel. DM10/DM20 are for 4-cylinder petrol engines only. For diesel engines, the DM11/DM12/DM20D models are available. The fastening of these tachometers is also carried out on double-sided tape.
Amfiton-219/250
These models are distinguished by their spectacular appearance and indication with color zones depending on the load on the engine. They are intended only for carbureted four-cylinder engines. Additional features include a voltmeter, battery charge level meter and voltage regulator control. Amfiton-250 is also equipped with a timer and UZSK. These models are larger than the previous ones. Another disadvantage of this series is the limited measuring range: 400 - 5990 rpm.
Connection - petrol engine
In the case of a gasoline engine, an automotive electronic tachometer is connected in the following order:
- The black contact wire must be connected to the "mass" of the car.
- The red wire connects to the ignition switch terminal. Thus, when the ignition is on, the device will receive a voltage of 12 V.
- The connection of the third wire, which may have different colors, depends on the type of ignition system on a particular vehicle. With a contact ignition system, the connection is made through a breaker-distributor. With a non-contact system, the wire is connected to the voltage switch or to the output of the ignition coil.
- If a backlight is provided in the tachometer, it closes to the side lights power wire.
- If there is a voltmeter among the additional functions of the device, it has a separate wire that must be connected to the "plus" of the battery.
Connection - diesel engine
On vehicles with a diesel engine, the connection sequence is as follows:
- It is necessary to remove the protection of the generator. Usually access to it is difficult, so to dismantle it, you will need to drive into an inspection ditch, overpass or use a lift.
- The output wire must be connected to the generator terminal marked with the letter "W". If there is no such terminal, then the only option is to disassemble the generator. Then one of the wires coming from the winding to the generator rectifier is disconnected. This wire must be connected to the tachometer wire and insulated. Then the generator is assembled and installed.
It is recommended to additionally close the contact of the oil pump, otherwise, false operation of the emergency oil pressure lamp may occur when a certain wheel speed is reached.
Get the tachometer and suitable terminals. You can buy and install both a new device (its price is in the range of the equivalent of $ 30-50), and an inexpensive used tachometer.
- The only extra you need is a set of quick connectors. You can buy them at any auto electric store for the equivalent of $2-$3. Keep in mind that the wire size is usually 0.5-1.0 mm², so choose the right size terminals.
Set the tachometer to the number of cylinders in your engine. New tachometers are usually designed to work with four-, six- or eight-cylinder engines. To adjust, you need to remove the cover from the back of the device, under which the switches for setting the number of cylinders are hidden.
- Move the switches to the correct position for the number of cylinders in your engine. Remove and install the cover carefully so as not to damage the internal wiring of the tachometer. If necessary, use a screwdriver in the process.
- Most often, there are only two switches - No. 1 and No. 2. In most cases, the scheme is as follows: for a four-cylinder engine, both switches must be moved down, for an eight-cylinder, both up, and for a six-cylinder, No. 2 down and No. 1 up. Be that as it may, if you have a new tachometer, then carefully study the instructions before setting it up.
Locate the ignition distributor (distributor) output wire under the hood. Depending on the design of the motor, either AC or DC current can flow through this wire; the same applies to other wires connected to the tachometer (ignition, light, etc.). It is very important not to confuse anything and connect exactly the wires that are required to the device. Therefore, for a preliminary check, you may need a multimeter and a car repair manual with an electrical circuit.
- It should be noted that some new tachometers are not compatible with high-voltage solid-metal conductive wires, so connecting the device without first reading the instructions can be dangerous.
Check connection. Before finally installing the tachometer on the steering column, it would be a good idea to hook up all the wires, start the engine and make sure everything works as it should. Do not drill mounting holes without testing the correctness of the connections. If there are no problems, then after connecting all the wires of the tachometer (including the ground), the device, after starting the engine, should give an accurate value of the engine speed and change the readings as you press the gas pedal.
- Connect the tachometer to ground. Connect the earth wire coming out of the device to the car body. It is not necessary to pull the wire all the way to the negative battery terminal. Almost the entire body of the car is already connected to this terminal with a thick cable. Just run the tachometer ground wire to the point on the body where it will be more convenient to connect it.
- Connect the appropriate tachometer wire to the output of the ignition distributor. The peculiarity of this wire is that it will have to be passed through the partition of the engine compartment, since it must go directly to the engine. The location of the connection point for this wire may vary depending on the engine.
