Speedometer - this is the component that no car can do without. Using this mechanism, you can accurately determine at what speed the vehicle is moving. According to the rules of the road, driving with a broken element in a car is prohibited. Any driver should know how to replace this element and identify this malfunction. So, let's look at what the 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 such until the 90s.
Closer to the "zero" on the machines began to install electronic
speed sensors. The type of cable also depends on the type of instrument cluster. This item is located in the gearbox. The speedometer cable (including VAZ-2113) reads data from the transmission shaft and transfers information to the instrument panel. So the driver can control the speed of the car in real time.
Device
The device also includes an odometer.
With it, you can read information about the mileage of the car. There are two scales on the dashboard. The one on top is responsible for the full mileage of the car, and the bottom - for the daytime (up to a thousand kilometers). All readings are read from the cable. The speedometer and odometer are directly related. The design of the element involves the presence of high-speed magnetic nodes. Due to the force of rotation of the magnet, a stream of eddy currents is formed. Passing through the coil, currents create a magnetic field. Thus, the arrow of the speedometer on the dashboard begins to move on 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 gearbox. On
rear-wheel drive cars, it also acts as 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 gets 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, tire profile and
gear ratio of the gearbox (if it is a car with rear-wheel drive) affect the speedometer. Different bridges are put on absolutely identical cars from the factory, with a different gear ratio (an average of 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 replacing it is much easier (you just need to
disconnect one block with wires).
Major malfunctions
A part such as a speedometer drive cable is highly reliable. But you should not exclude 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? You do not need to replace the speedometer cable. The reason may be a banal loosening of the nut, which secures the flexible shaft to the drive. In this situation, the winding of the speedometer will help , or rather, tightening the nut itself. In half the cases, the problem goes away by itself.
But there are more significant malfunctions, in which only speedometer repair or its complete replacement will help. So, the drive shaft itself fails. It breaks off. The malfunction is accompanied by a characteristic knock. The arrow stops showing reliable information. What could be the reason for this? Drive breakage occurs due to the presence of contamination inside it. The counter spring also ruptures. In any case, it is necessary to replace the speedometer cable (if operations with a nut tightening did not help). Below we will look at how to change this element with our own hands.
Dismantling
First of all, you need to remove the old mechanism. To do this, de-energize the vehicle'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, find the connection point of the mechanism and unscrew the fixing bolt that fixes it. Regardless of whether the front or rear wheel drive car, the end of the cable is on the gearbox. For convenience, it is better to use a viewing hole. So, we unscrew the fixing bolt and remove the clamping nut that connects the cable to the speedometer in the cabin.
Next, go to the second part of the dismantling. To completely remove the element, you need to partially disassemble the instrument panel. From the reverse side we take out the second end of the cable.
When disassembling, be careful not to damage the rubber gasket.
Installation
The installation order of the item is the reverse of removal. To do this, 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. If this is a front-wheel drive car, where the gearbox is installed in the engine compartment, the mechanism is routed through a special hole in the partition between the passenger compartment and the “engine compartment”. All rubber seals are installed in place. Depending on the brand of car, there may be a different number of them (but in any case at least two).
Useful Tips
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. It is not permissible to use elements shorter or longer than the standard value.
- Before installing a new speedometer cable, it is recommended to apply a layer of lubricant on it. This will exclude premature failure of the mechanism. You can use conventional mining or Nigrol.
- When installing, try to lay it as from the factory. The cable must not come into contact with moving parts. It is also impossible to use tight loops when laying. So you increase the load on the core of the cable, and it will quickly fail even with a good layer of oil.
Speedometer winding
We’ll tell you a few words about such a device as a “twist” for a speedometer. The element is designed to rewind the odometer. It is connected via the OBD diagnostic connector . The device intervenes in the control unit and winds up the mileage readings on its own. The device is based on the CAN bus. Mileage is adjusted not only on the dashboard, but also in all duplicate blocks. Determining the wrapping with such a device is quite difficult. Who uses such devices? They are used on host 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 computer. The cost of such a device is 3.5 thousand rubles.
Repair or replacement?
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 whole element. Moreover, suitable repair kits are not always available.
Customization
So that the speedometer readings were 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 end of the cable. The normal parameter is 65 millimeters with a margin of 5 mm. If your readings are different from the factory, you should adjust the tension of the cable with a wrench using a lock nut. After that, you can start operating the car.
Conclusion
So, we found out how the speedometer cable is arranged and how to replace it with our own hands. As you can see, this is a very necessary element, without which driving in any car becomes unsafe. Indeed, it is not always possible to determine speed subjectively, especially if you are moving along a wide highway.