Speedometer cable and its replacement

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:42

Speedometer - this is the component without which no car can do. With this mechanism, you can accurately determine how fast the vehicle is moving. According to the rules of the road, it is forbidden to drive with a broken element in a car. Any driver should know how to replace this element and identify this malfunction. So, let's look at what a speedometer cable is, how it works and how to replace it.

Characteristic

It should be noted that this element is used only in mechanical speedometers. All cars were equipped with these until the 90s.

Closer to "zero" cars began to install electronic speed sensors. The type of cable also depends on the type of instrument cluster. This element is located in the gearbox. The speedometer cable (including VAZ-2113) reads data from the transmission shaft and transmits information to the instrument panel. So the driver can monitor the speed of the car in real time.

Device

The mechanism also includes an odometer.

It can be used to readvehicle mileage information. There are two scales on the instrument panel. The one on top is responsible for the full mileage of the car, and the one below - for the day (up to a thousand kilometers). All indications are read from the cable. The speedometer and odometer are directly linked. The design of the element assumes the presence of high-speed magnetic nodes. Due to the force of rotation of the magnet, a flow of eddy currents is formed. Passing through the coil, the currents create a magnetic field. Thus, the speedometer needle on the instrument panel begins to move along the scale. The force of rotation is proportional to the frequency with which the magnet rotates.

When reviewing the device of such an element as a speedometer cable, the question arises: how does the arrow not fall if the gear ratio on the shafts of the box is different? Everything is very simple. Inside the element is a small reducer. On rear-wheel drive vehicles, it also performs the function of a secondary shaft. The position of the arrow on the scale depends on the strength of the magnetic field in this gearbox itself. So the driver receives accurate information about the mileage and current speed of the car.

Is there an error

It is worth noting that the readings on the instrument panel (if it is a mechanical element) may differ slightly from the real ones. But often the error does not exceed five percent.

So, the size of the rims, the profile of the tires and the gear ratio of the gearbox (if this is a rear-wheel drive car) affect the speedometer readings. Different bridges are put on absolutely identical cars from the factory, with a differentgear ratio (average ranges from 3.9 to 4.4 for classic VAZs). Therefore, many manufacturers began to abandon cable speedometer technology. Now cars use an electronic sensor. Its error does not exceed one percent. And it is much easier to replace it (you just need to disconnect one block with wires).

Main malfunctions

Such a detail as a speedometer drive cable is highly reliable. But it is not worth excluding problems with this mechanism (especially since the technology is very outdated). So, during operation, the arrow on the instrument panel may twitch or even stop responding to changes in speed. How to be in such a situation? It is not necessary to replace the speedometer cable. The reason may be a simple loosening of the nut that secures the flexible shaft to the drive. In this situation, winding the speedometer will help, or rather, tightening the same nut. Half the time, the problem goes away on its own.

But there are more significant malfunctions, in which only repair of the speedometer or its complete replacement will help. So, the drive shaft itself fails. It cuts him off. The malfunction is accompanied by a characteristic knock. The arrow stops showing reliable information. What could be the reason for this phenomenon? The breakage of the drive occurs due to the presence of contaminants inside it. There is also a rupture of the counteracting spring. In any case, it is required to replace the speedometer cable (if operations with tightening the nut did not help). Below we will look at howchange this element with your own hands.

Dismantling

First of all, you need to remove the old mechanism. To do this, you need to de-energize the car's on-board network by removing the negative terminal from the battery. Next, disconnect the old element. How to remove the speedometer cable with your own hands? To do this, you need to find the junction of the mechanism and unscrew the mounting bolt, which fixes it. Regardless of whether the car is front- or rear-wheel drive, the end of the cable is located on the gearbox. For convenience, it is better to use a viewing hole. So, unscrew the mounting bolt and remove the clamping nut that connects the cable to the speedometer in the cabin.

Next, proceed to the second part of the dismantling. To completely remove the element, you need to partially disassemble the instrument panel. On its reverse side, we extract the second end of the cable outward.

Be careful not to damage the sealing rubber when removing.

Installation

The order of element installation is reverse to removal. To do this, we lay a new speedometer cable through the panel in the cabin and “pull” it to the transmission. Try to fix the element in the same way as the old one lay. If this is a front-wheel drive car, where the gearbox is installed in the engine compartment, the mechanism is laid through a special hole in the partition between the passenger compartment and the engine compartment. All rubber seals are installed in their places. Depending on the brand of car, there may be a different number of them (but in any case, at least two).

Usefultips

When performing operations with this mechanism, pay attention to the following points:

• When buying a new item, be sure to check the cable length. On the same car models, its size may be different. Items shorter or longer than the standard size are not allowed.
• Before installing a new speedometer cable, it is recommended to apply a coat of grease to it. This will prevent premature failure of the mechanism. You can use regular mining or "Nigrol".
• When installing, try to lay it in the same way as from the factory. It is unacceptable for the cable to come into contact with moving parts. Also, tight loops should not be used when laying. This will increase the load on the cable core, and it will quickly fail even with a good layer of oil.

Speedometer winding

Let's talk a few words about such a device as a "twist" for a speedometer. The element is intended for winding up odometer readings. It connects via the OBD diagnostic connector. The device intervenes in the control unit and independently winds up the mileage readings. The CAN bus is used at the heart of the device. The mileage is adjusted not only on the instrument panel, but also in all duplicate blocks. It is quite difficult to determine the wrapping using such a device. Who uses these devices? They are used on the owner's cars in order to "weld" on fuel. So, the car travels 100 kilometers, and the mileage of 110 is displayed on the instrument panel and in the ECU. The cost of such a device is 3.5 thousand rubles.

Repair orreplacement?

If you are in doubt whether to repair the speedometer or completely replace it, you should pay attention to the price of the mechanism.

On average, its cost does not exceed two hundred rubles. Therefore, it makes sense to replace the entire element. Moreover, suitable repair kits are not always available.

Settings

In order for the speedometer readings to be with a minimum error, experts recommend making additional adjustments. To do this, measure the distance from the beginning of the damper to the clutch fork. The parameter should be 86 (+5) millimeters.

Next, measure the gap between the end of the damper and the tip of the cable. The normal parameter is 65 millimeters with a margin of 5 mm. If your readings differ from the factory ones, you should adjust the cable tension with a wrench using a lock nut. After that, you can start operating the car.

Conclusion

So, we found out how the speedometer cable works and how to replace it with your own hands. As you can see, this is a very necessary element, without which driving any car becomes unsafe. After all, it is not always possible to determine the speed subjectively, especially if you are moving along a wide highway.