Why in the car odometer?

Если отвечать кратко на вопрос, what is the odometer in the car, то можно сказать, что это небольшое устройство в автомобиле, которое фиксирует пробег, или километрах машины. Одометры могут быть электронными и механическими, и в зависимости от этого у них различается разный принцип работы.

The principle of operation of the mechanical odometer

odometer what is it

Механический odometer имеет редуктор 1690:1, то его входной вал должен провернуться 1690 раз, чтобы на табло появился один километр. Вращается он гибким кабелем, сделанным из туго скрученной пружины. Кабель находится внутри металлической трубки в резиновом корпусе, вращается он выходным валом коробки передач, а подключен к приборной панели, где и соединяется с входным валом odometerа.

In the odometer itself, a series of three worm gears is used (by hooking the worm and the worm wheel associated with it). The inlet valve drives the first “worm”, which already drives the transmission.

One complete turn of the worm turns one prong. Then the same mechanism sets in motion the next “worm” that turns a different gear, which sets in motion the last “worm” connected to the odometer indicator and turning the number with tenths of a mile.

what is the odometer in the car

Each indicator has a series of studs that stick out on one side, and two more studs sticking out on the other side. As soon as these two studs fit into the white plastic gear, one of the teeth falls between the studs and rotates with the indicator until the studs pass further. One of the indicator studs with a large number takes part in the mechanism, making 1/10 of its rotation.

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Mechanical odometers can be rewound. We'll talk about how to check the “honesty” of the odometer a little later. In the meantime, let's deal with another type of it, so that the question of what it means is probably no longer a question.

Digital odometer

что такое odometer

His system uses a gear wheel, which is mounted on the input shaft of the gearbox and a magnetic sensor, counting pulses every time one of the wheel teeth passes by. There are also machines that use slotted wheels and an optical sensor. In any case, the auto computer knows exactly what distance the car travels between each pulse, and uses it to update the odometer reading.

Information about the distance traveled to the dashboard enters through the wire connection of the engine control unit. It reads all pulses and also tracks the total distance traveled by the machine. Therefore, it is impossible to unscrew the digital odometer back: the value that is stored in the engine control unit does not coincide with the desired, which is impossible. And this value can always be checked with the help of computer diagnostics in any service center of the official dealer.

Odometer "honesty" check


Now that it has become clear that this is an odometer, you can move on to the important question of checking the “honesty” of this device. It is necessary to understand the question, since the procedure of twisting the odometer is not difficult, which is why it is often used in practice. In each VAZ 2109 (tuning) before selling a car, many car owners twist the odometer, which will reduce the apparent mileage of the car.

Any mechanic knows that for this you need to disconnect the speedometer cable from the gearbox, rewind in the opposite direction using, for example, an electric drill, set the cable into place when the mileage has reached the desired figure. Recognizing such an intervention is difficult.

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You can climb under the bottom of the car and check the speedometer drive nut: if it was recently unscrewed, it will be clean, and there will be dirt and dust around, at the gearbox. But if the mileage is dropped by temporary separation of the gears of the counting mechanism of the testimony, it will be impossible to detect twisting.