Speedometer - a device designed to measure the velocity of the car. IN modern automotive industry Used mainly electronic variety of instrument.
Domestic automotive industry Started apply electronic speedometer Since the release of the VAZ-2110, the power system is based on the injector.
Therefore, if the speedometer does not work even on relatively old cars, the reason should be sought in electrical wiring elements.
The speed measurement system in a modern car includes such elements as:
- Speed \u200b\u200bsensor installed in the checkpoint;
- Electronic motor control unit;
- Speedometer scoreboard on the instrument panel;
- Wiring.
During the operation of the engine and the gearbox, the sensor removes information about the frequency of its rotation from the output shaft of the gearbox, and transmits it into the ECU as an electrical pulse. The higher the vehicle speed turns out, the shorter the time interval between the sensor signals.
The electronic control unit calculates the speed of the machine based on the frequency of the pulses received. This is the principle of operation of the speedometer electronic type. In parallel with the correction of the engine operation modes, the control unit transmits information about the speed of the auto movement on the speedometer and the diagnostic shoe. 
If there is a route computer with "to" the output of the DC, the speed data can be duplicated on its scoreboard.
Causes of Speedomera malfunction
If a speedometer stopped working, the troubleshooting is carried out in several directions. The cause of refusal can serve the following breakdowns:
- Failure of the speed sensor;
- Electric wiring damage;
- Oxidation of "mass" contacts;
- Malfunction of the Speedometer itself;
- ECU malfunction;
- Incorrect installation of the instrument panel after removal.
As a rule, no other causes of malfunction is detected. Sometimes the device failure is due to the combustion of the fuse of electrical circuits responsible for the operation of the dashboard. However, this problem can be attributed to the discharge of electrical wiring faults.
The diagnostic feature of the fuse destroyer F19 is:
- Failure of the entire instrument panel;
- Failure of the diagnostic unit;
- Failure of the system of automatic door lock;
- Reversing reverse lamps.
Diagnostics
Fault diagnostics start with disconnection of wire blocks from the harness of the speed sensor and their check using the check light bulb.
For the manufacture of light bulbs - the checks, any car lamp is needed, capable of operating at a voltage of 12 V, and two wires with a length of about 1 meter each. One of the wires is fixed on the plus, the second - on the minus lamp output. Also, the obtained device includes a Crohn battery. 
For checking one wire control lamp Fixed on a body weight or rechargeable battery, and the second is carried out short frequent touch to the average contact of the DS connector. In the absence of malfunctions on the plot, the connector is a speedometer, the latter's arrow will slightly slightly tap or lifted. If the arrow aggregates, the answer to the question why the speedometer does not work, can be considered found - the speed sensor requires replacement.
In cases where the reaction of the arrow on tapping on the central contact of the pads cannot be identified, it is necessary to produce a "ring" of the speedometer power chain. The procedure is carried out using a multimeter (multitetester), or by using all the same light bulbs.
Pre-harness the wires are disabled not only from the shoe of the speed sensor, but also from the speedometer itself. One tester or control lamp is connected to the end of the wire, which is under the hood, the other to the cabin end of the speed chain of the speed meter.
If the test tester indicates a violation of the chain integrity, further troubleshooting is carried out in this direction. It is necessary to check the fuses, the locations of the wires, their integrity insulating the insulating braid.
The search zone can be reduced, gradually "nicknamed" individual sections of the chain. On the model 2114 and other products of the vase, the cause of the speedometer failure often becomes the oxidation of "mass" contacts fixed on the car body.
In cases where the speedometer arrow does not work, but there is no data on malfunctions of an electric power supply circuit, a legitimal conclusion is made to malfunction of the device itself. Additional check can be made by temporary installation of an obviously good dashboard. 
Repairs
Repair of the speed measurement system directly depends on the identified malfunction:
Speed \u200b\u200bsensor
- Clear contamination;
- Clear contacts from corrosion and oxides;
- If the measures described above did not help, the sensor is replaced.
Wiring
- Check and clean "mass" contacts;
- To solder or fasten with the help of a "twist" of the fracture of the wires, due to which the speedometer stopped working;
- Close the insulating tape of the place of damage to the braid;
- Replace fuses failed;
- Clear the pads from the oxides and corrosion.
Speedometer
If a speedometer stopped working, it is replaced. On the domestic carscollected using the electronic type of speed meter, the speedometer changes with the instrument panel. You can carry out this operation yourself. For its execution, only the cross screwdriver and passage will be needed.
It is impossible to restore the efficiency of the device. It is able to make a master electronics. However, considering quite low rates for spare parts for cars russian modelsThe appeal to the master is economically inappropriate.
Repair of the old speedometer may be much more expensive than full replacement The old combination of devices for a new one.
Speedometer, as follows from the name, shows the speed of the car. Compliance speed \u200b\u200bregime It is important not only to avoid fines, but also for making safe turns and other maneuvers. The higher the speed, the larger there should be a radius of safe turn. If the radius is less necessary, the likelihood of car care is large in the skid and tipping car. Therefore, the cost of the speedometer is as important as the quality operation of the steering or braking system.
How speedometer works
There are two main modifications of speedometers:
- mechanical;
- electronic.
The principle of operation of a mechanical speedometer is to transform the rotational speed of the shaft into the energy that shifts the arrow. Speedometer drive is located in mechanical or automatic box Transmission and connected to the indicator with a flexible metal cable protected. The tips of both sides of the cable are made in the form of a tetrahedron, which effectively transmit rotation from the actuator to the indicator. The mechanical speedometer is always connected to the odometer (indicator of the car run) and is a single block with it.
The principle of operation of the electron speedometer is a sensor that produces pulses of a certain frequency and duration (depends on the velocity of the car). The sensor is attached either to a separate electronic speedometer or to the on-board computer. Both the computer and speedometer perform the same function - calculate the number of pulses per unit of time and convert the value to clear kilometers or miles per hour.
Speedometer malfunctions
Most often are the following malfunctions:
- cliff or damage to the cable;
- cracking the tip of the cable with the slave gear;
- malfunction of a mechanical or electronic indicator;
- malfunction of the pulse sensor;
- bad contact or wire breaking, which connects the sensor and indicator or computer.
Video - how to fix the speedometer
Mechanical Speedometer Diagnostics and Repair
- For diagnostics, you will need:
- motor 12 volts;
- flat and cross screwdriver;
- flashlight; jacks and stands;
- instructions for repair or maintenance of your car.
To check the speedometer, lift the front passenger side of the car with the help of a jack. About how to do it safely, read in the article (replacement and restoring shock absorbers). Remove the front panel (torpedo) to get to the instrument combination. On some models of cars, you can do without this operation, so carefully examine the instructions for the repair and operation of your car. Remove the combination of instruments and unscrew the locking nut of the cable from the indicator, start the engine and turn on 4 transmission. Check if the cable is spinning in a protective casing? If so, muffle the engine, insert and tighten the cable tip, then start the motor again, turn on 4 transmission and look at the indicator readings. If the arrow does not change the position, the indicator is defective, it must be replaced.
If, when the engine is running and enabled, the cable does not spin, it is necessary to drown out the motor and remove the rope from the drive located on the drive gearbox. Pull out the cable from the boost space and inspect the tips, whether the form (square) is damaged. Screw the tip on one side of the cable and watch the tip of the other side. If both tips rotate synchronously, without the effort and the verge of tips are not muffled, then the problem is in the worn gear of the drive, so it must be replaced. This operation is described in the instructions for the repair and operation of the car.
Diagnosis and repair of electronic speedometer
For diagnosis and repair you will need:
- flat and cross screwdriver;
- tester;
- a set of keys;
- scanner for injector Engine (Instead, you can use the usual oscilloscope).
Run self diagnostics on-board computer (BC). In most injection cars, which were produced after 2000, the BC supports this feature. If the BC gives an error, it is necessary to decrypt it using a special table that is in the maintenance and repair instructions for your car. But, the diagnostic results will be shown, the entire speedometer system works, or not. To eliminate malfunction will have to search for damage yourself. To do this, lift the car as described above. Attach the oscilloscope to the average contact of the speed sensor (installed on the speed meter drive) and the plus contact of the battery. Get the engine and turn on 1 transmission.
A good sensor will produce a pulse signal with a voltage of at least 9 volts with a frequency of 4 - 6 hertz. If the sensor is working, it is necessary to turn off the transmission and use the tester to check the wire that connects the sensor with the controller of the electronic control unit (ECU). Or with an oscilloscope, check the sensor signals at the entrance of the ECU. If there are signals, you need to check the terminals and wire that connects the computer and the combination of instruments (the speedometer indicator). If there is a special scanner, it is advisable to check the speedometer indicator, this will make it possible to more accurately determine the cause of the fault.
The whole speedometer ceases to work due to falling into the terminals of water and dirt, as well as due to the cliff or fracture of the signal wires. Therefore, in most cases, it is enough to dry and clean the contacts. If the results of the verification will cause a speed sensor malfunction, it will be necessary to replace it. This procedure is detailed, as well as replacing a damaged indicator, described in the instruction manual and repair your car.
The article describes the simple generator on the 555th timer, with which you can check the performance and correctness of the readings. electronic speedometersExtracts an electronic Hall Sensor as a speed sensor.
In many modern carsmobile, such as Gazelle (GAZ 2705, 33021), "Volga", KRAZ and other electronic speedometers with a microammeter and a stepper motor. Such speedometers work complete with electronic sensor Hall installed on the gearbox. When the car is moving, the sensor is driven by the gear of the secondary shaft of the gearbox. In one turn of the shaft of the sensor, six pulses are produced electric current.
These impulses go to the speedometer scheme. The speedometer speed indicator is a micro ammeter. In addition, the reinforced representation pulses are fed to the stepping motor that rotates the drums of the route traveled.
According to the technical documentation with which it is possible to read in, to check the serviceability of such a speedometer, it is necessary from the G5-54 signal generator to enter the connection to the Hall sensor speedometer, the rectangular form of a positive polarity amplitude of 6 ... 7 V, duration 200 ... 250 μs and a frequency of 100 ... 200 Hz.
If a high accuracy of testing of speedometers testing is not important to the user or track execution of the fleet, and it is only possible to check their performance, the design of a simple generator of rectangular pulses can be easily cope with this task.
Principal electrical circuit The generator is shown on fig.1. It is assembled on the universal timer 555 chip. Inclusion scheme is typical. The nominal elements C2, R2-R4 are selected in such a way as to obtain a meander with a frequency of 100 ... 200 Hz. The required frequency of the pulses of the assembled generator can be adjusted by the R3 stroke resistor. The scheme is designed to use in vehicles on-board network 12 V. If the voltage of the car on-board network is 24 V (for example, to the KRAZ), then the scheme must be supplemented with an integral stabilizer DA2, including its power circuit in the gap, as shown in the dotted line.
Design and details
All elements of the scheme are assembled on the printed circuit board from one-sided foil fiberglass with dimensions of 30 × 20 mm. The drawing of the printed circuit board and the location diagram of the elements are shown in Fig.2. For ease of repetition, the drawing is shown from the foil side. In the design, output radiocompunists installed vertically are applied. Special requirements for them are not presented. Conductors are soldered to XT points 1-CTH, on the other end of which a connector is installed, a similar connector connecting the Hall sensor. All necessary for the operation of the chain generator are displayed on this connector: plus / minus power and speedometer. The printed circuit board is installed in a suitable electrically isolated case. The author used for this purpose a segment of a plastic cable box with a cross section of 25 × 16 mm.
Assembly, adjustment and use
The correctly assembled generator in the setup does not need. It should be paid to the correct connection of the connector conclusions, since when the supply voltage is accidental to enter the generator output, it will be released from:; 0 building. To configure the device, there is no need to use radio measuring instruments. It is enough to have a well-good speedometer. The device is connected instead of the Hall sensor and the R3 trim resistor achieves the desired speedometer reading, for example 60 km / h. If the regulation range is not enough, then to increase the boundary frequency of the generator, it should be slightly reduced resistance to the resistor R4, and to reduce it - increase.
Most car enthusiasts prefer to buy cars on secondary market. So you can save considerably and buy a decent car for a little money. But it is not always possible. Trying to overestimate the price, unscrupulous sellers deliberately twist the car mileage. You need to know how to determine it visually and with the help of technology. In the article, we will look at how to check the mileage of the car (twisted or not) and what nuances should be paid attention to.
What do you need to be afraid?
Adjusting the odometer readings is absolutely on all vehicles.
Even 2-3-year-old machines are subject to testimony. Do it, as a rule, greedy vendors who want to hide all the shortcomings of the car, trying to "fall" him at an overpriced price. Inexperienced drivers often come across this.
How to check whether the car mileage twisted? It can each, you just need to carefully examine the car. What should be afraid when buying a car with twisted mileage? Buying a car with a small mileage, you risks to take real auto balls, which will demand a lot of money from you for service. So, the adjustment of the odometer is often produced when run from 90 to 110 thousand. And this is due to the fact that in this period of time the car passes the largest scheduled maintenance. In order not to spend money on the repair, the unscrupulous sellers screw the numbers of the odometer and set the vehicle for sale, convincing the buyer that the car has already passed all the necessary then.
Determine whether mileage is twisted: how much is cheating?
Milometer often reduce on a quarter. Thus, the car, which passed, according to the seller, 200 thousand kilometers, this mileage is 240 thousand. But there are other meanings, because when adjusting can be set any digit, at least 6 units.
It all depends on the conscience of the seller. Although in fact this action is fraud and is punished, every second car in the secondary market - with a twisted "counter". You can not believe the numbers on and the seller's words in no case. The famous proverb says: "Trust, but check."
Electronic odometer
It is believed that such a counter is impossible to twist. In fact, the adjustment is possible both on classical mechanical odometers and on modern electronic. Of course, the most the best way - It is to go to the diagnosis to official dealer. But what if the buyer does not have such an opportunity? How to check whether the car mileage twisted?
Computer diagnostics
This is perhaps the most faithful and fast way Odometer readings authentication. This requires a laptop and OBD-2 cord. Connecting you can see the real mileage of the car. Be careful! Some sellers produce correction with dumping data in the electronic unit.
How to check the mileage of the car (twisted or not)? To make sure the authenticity of the kilometer has passed, we look at individual knots. The mileage is recorded not only in the engine and box, but also in small systems (for example, light control unit). And they are most often protected from overwriting. Here we can catch the seller "on the hook", pointing to him on the right mileage. But there are other ways to find out real mileage car. Let's look at them further.
How to find out whether mileage is twisted? Dashboard
Pay attention to how the front torpedo was collected and dashboard. If he had traces of disassembly (and these are scratches and tidy a screwdriver), that is, the reason to think about it. By the way, the dashboard itself with back side covered with a thin layer of varnish. If the mileage twisted, it will be visible immediately. But for this you have to completely remove the shield out.
If it is a classic odometer with a drum mechanism, pay attention to the gaps between the numbers. They should not stand crookedly or with different remoteness from each other. Otherwise, there are all reasons for confirming the adjustment of a kilometer.
Salon details
We continue to tell how to check the mileage of the car (twisted or not). An important detail when inspection - steering wheel. According to his state, it is possible to determine how much the testimony of the odometer correspond to reality. car? The steering wheel begins to stick at 250 or more than a thousand kilometers. And early wear can not be written off poor quality assembly.
The car with such a steering wheel, as in the photo, definitely can not be a run below 100-150 thousand kilometers. Also note that the sellers are stirred steering wheel, and often use cheap materials for this. If it has no factory line, it means that the element has been restored.
Do not deprive the seat and seats.
It will be difficult to alter them. Yes, you can do it, but it will not pay off when selling it. Some set the seats with disassembly, shot from cars on which mileage is less. In this case, pay attention to the adjacent chairs and the rear row.
If the wear on them is more than on the driver, it means that the seat changed. Some sellers to hide wear, cling "T-shirts" or covers. Do not be afraid to look under them. Perhaps the owner tried to hide traces of wear.
Another factor is the trimming of the doors. There are few things in this trifle from sellers. Often, their deception ends on the adjustment of the odometer readings and reset the main data from the ECU. No one will "bother" the state of the door sheath and the handles. When buying, pay attention to these details.
Also inspect the condition of the lever and the cover of the handle parking brake. Noticeable traces of wear on them appear no earlier than in 200 thousand kilometers.
Pedals.
Another trifle about which sellers forget is a state of pedals. Often the original linings are not available, so the car is sold with erases. They wear out too with substantial mileage. On one hundred thousands they should not be "lys".
Do not be fooled on a beautiful wrapper
So that the car seemed as attractive as possible, his body tinted. However, do not rush to determine the honesty of the mileage in quality paint coating. If a body repair It was performed qualitatively, to determine it is not even an experienced motorist. The only thing that can be done is to check the LCP thickness using a thickness gauge. He also determines how much put putty on the body (if the car was after an accident). The mechanism "breaks" the distance from the top of the LCP to the metal.
However, look at the quality of painting, checking the twisted mileage, does not make sense. After all, an accident may happen at any kilometer. It all depends here on how qualitatively a repair was made. Well, if you buy a car with age 20+, inspect hidden places - thresholds and technological plugs on the bottom. Corrosion does not depend on the run, but rust is a significant reason to reduce the price.
If a car is up to 3-5 years
How is the car twisted or not, on relatively "fresh" machines? Ask the seller service book. It should be noted here, on which mileage was produced, then and what works were made. If such a book is there, it is a big plus. Such a seller has no intention to deceive the buyer.
So, we found out, we hope the information provided will help you avoid deception.
It was not bad in the old days before people did not get the question "how to find out whether mileage was twisted" When the buyer raised the issue of buying a vehicle. I woke up early in the morning to go to the fair, walked around the rows, looked in my teeth and began to bidding for the stallion liked. And after the long-awaited shopping and home is not a shame. If anyone does not understand why to look into the teeth, I will explain: the teeth were always a reliable indicator of age. No matter how good the horse did not look like an external data, but it was the teeth that he always gave her age.
What do we observe these days?
Upon arrival at the nearest car dealership, which sells used cars, you can see unique beauty: all cars, both on the selection, clean, mirrored and are ready to meet with their new owner. And where, and most importantly, to watch in the teeth? Unfortunately, not everything is so simple in our lives. Otherwise, I could with a great deal of confidence rely on the speedometer testimony, which, indeed, shows how much our horse drove, and not to think how to check whether mileage is twisted. But, in our time, learned to fake horsepie teeth, what to say about iron horses. Want to check it out? Hurry up to place an ad for the sale of your car, how will call calls with proposals for a certain cost to twist the mileage of your car immediately sprinkle. How do you like?
So, it's time to move to the main theme of our conversation. The so-called corrective actions relating to the mileage of cars are made by special intervention using a specialized tool or the same equipment to the vehicle nodes. This is done in order to change the side of the side computer or the boards with the instruments.
Not so long ago, when speedometers were mechanical and, respectively, to them correction methods. In the process of all the case, the Speedometer node itself and the manual exhibition of the necessary numbers were either operated with the help of electric drills. A cartridge of an electric drill was carefully dressed on the edge of the device, after which the necessary mileage was screwed. To date, most of the automobile units have become electronic, i.e. and the mileage is adjusted using electronics. It happens like this: specialized equipment is connected to the diagnostic connector, and refractming new numbers. Some five minutes of work and your car can with the extraordinary ease of its owner to reincarnate from a pensioner with considerable experience in a middle-aged man who travels only on weekends. How to be and what needs to be done not to become deceived?
We propose to direct all your attention to those explicit signs for which without much difficulty can be guessing about false mileage testimony.
- Different data in the testimony between speedometer and other electronic blocks Auto.
It's no secret that today's car manufacturers with help electronic methods Record the run of the car simultaneously into several different electronic blocks. Not bad, right? In many cases, the speedometer itself can be adjusted to the data adjustment, when in such blocks as ABS or automatic automatic transmission, the attacker will not reach. Often, careless craftsmen simply forget to flash the ignition key, in which all representatives of modern cars also have a run data. In imperative interference in electronic system Car, there may be traces indicating outside intervention, helps to answer the main question how to determine the twisted mileage ...
One of the negative sides of this method is the presence of a highly specialized tool, which may be in places involved in maintenance.
- Different data in the testimony between the speedometer and the saved service maintenance history, plus the testimony of official dealers.
And immediately give an example from life in practice, showing one of the ways how to check the twigs or not.
Potential buyer Insperse cars on a speedometer of which just over 50,000 km. After opening the hood, the buyer saw a tag indicating the last oil replacement. With careful reading it was possible to understand that the oil change was carried out at 120,000 km. When discussing that the data on run is clearly not coincide, the latter begins to "blush" and openly recognize in the deliberate twisting of the run. Of course, such a life example is too simple and quite understandable to everyone. Additional inconsistencies will help you find entries in the service book.
To this end, you should simply polish the appropriate order order, provided that they are preserved. A not bad and at the same time the current option will be a request for such information from an authorized dealer.
Any material, including leather products can specify the duration of the operational period. Translate a view should also be on the back of the seat. For example, minor gaps may appear no earlier than the run data will show 200,000 km.
Often can be seen as the sale of cars on its seat stretch covers, possibly hiding something important to you. For full information You can pay attention to the adjacent chairs in the car. In the event that the chair is pulled out by new leather, it is worth directly asking a question to the seller. The seat belt itself can be unandlied, as well as having small oversights.
- We study the features and external steering parts, the speed of switching the speed and armrest from the driver.
The steering wheel, as known to many drivers, is made of materials subject to time and mechanical exposure. Certainly, U. expensive cars The steering wheel is covered with skin. Separate attention should be paid to the lower part of the steering wheel, which is so often friction about the feet of the driver itself. This steering condition many sellers want to hide under decorating braid.
In addition, often the steering wheel simply shall be replaced by pursuing the goal of masking all the available defects and flaws of the car sold.
- What can hide the pedals?
One driver's leg almost constantly occupies the right pedal and in the case when it is a mirror in its own reflection, and the seller argues to the side of extremely rarely use vehicle - This is a sure way to think about the loyalty and the correctness of the words of the latter. In addition, the existing carpeted coatings tend to form holes. Think and threaten this information well. pedals will help you learn whether mileage is twisted on the car.
- Brake Disc Information
Wire resistance car disc Depends on many reasons. One of such reasons is, oddly enough, driving manner, a high-quality component of the disk and so on. There are average operating period of the discs: from 50,000 to 80,000 km. This data can be easily compared with car mileage.
- Status of the car sold
It turns out on average operating performance, the tread pattern is subject to wear for 50,000 km. It should also take into account the indices of the wear resistance of products of different model Row from different manufacturers. Analyze this information and relate with the fact that in front of you. The output will not make himself wait long.
- Timing belt
The required replacement regarding the timing belts should be carried out when run from 60,000 to 100,000 km. The state of the belt is easy enough to check, it is worth only to look under the hood. Next, all together analyze and compare with the words of the seller. The history of service can store information about its premature replacement. It is important to know that on some models of auto this belt hides the design of the protective casing. In this case, the belt should be inspecting additional equipmentwhich has the same operational deadlines for replacement.
- Squares, as especially visible defects in various parts of the car
How carefully did not try folk craftsmen to hide the real mileage of the car, but the presence of mechanical damage - Iron argument. For example, the surface of the hood has numerous chips, and also the owner for incomprehensible reasons decided to repaint it or was replaced windshield. Glass headlights closed significantly from the blows of small stones, etc. With such external characteristic Buyer will never believe in a small mileage of the car sold.
- The presence of a luft from the driver's door
How to determine whether the mileage is twisted on the door of the car? First open the door from the driver's seat. Next, unhurried movements try to shake it. It turns out that with the course of time the hinge doors tend to interfere, resulting in the so-called backy of free movement. On the new car, such problems can simply cannot. Additionally, you can check the doors from passenger seats. A vivid example of the fact that the driver "Takes" is the presence of a luft from the passengers and its absence from the driver's door.
- Notable traces from numerous opening and dismantling work in relation to the dashboard
Some of you call this indicator clearly outdated. However, we can't call it. With a mechanical species speedometer revealed dashboard With subsequent corrective actions. Today, this method practically no one uses or rarely enough.
In conclusion, I would like to summarize that all the above methods helping to make sure or are opposite to doubt the authenticity of the run indicators, are somewhat indirect. It is necessary to resort to their use to completely clarify the entire picture, but not separately. For example, if a man of complete physique is in the role of the seller, the fact of high wear of the driver's seat will talk about the mass of the human body, but not about twisted artificially by car run. Be vigilant and careful, carrying out the purchase of a car.
