Brake pad wear sensor: principle of operation, replacement, installation

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

The brake system is one of the most important components of any car. Its main elements are the disc and pads. Braking is based on the force of friction. The pads are in contact with the disc, resulting in resistance to torque. The car starts to slow down. However, over time, the friction material wears out and the pad needs to be replaced.

It is important not only to install these parts correctly, but also to diagnose wear in time. The brake pad wear sensor helps the motorist in this. The principle of operation, device, types - later in our article.

Characteristic

Based on the name, it becomes clear that the main function of this element is to determine the degree of wear of the friction material. A special lamp is displayed on the instrument panel. When the thickness of the pad approaches a minimum, the contacts close. The driver sees the corresponding signalon the instrument panel.

Views

At the moment there are several types of sensors:

• Mechanical.
• Electronic.

They can be installed on one or several vehicle axles. To find out their essence of work, we will consider each type separately.

Mechanical pad wear sensors

This is a fairly simple yet effective tool for monitoring friction lining wear. Such a brake pad wear sensor has a simple device and consists of a plate of a certain shape. It is installed on the base of the block. How does this element work? The principle of operation is as follows. The sensor plate is installed in such a way that its ends protrude beyond the block. When the friction material has worn down to a minimum value, this protruding end will begin to contact the disc. As a result, a characteristic creak will appear. Wear is determined from it.

On modern cars, the installation of a wear sensor for mechanical type brake pads is not performed, since they have a number of disadvantages. The first minus is the possibility of losing the plate. The second drawback is the frequent false positives of the mechanism. The element is located in such a way that dirt and other sediments adhere to it. Therefore, even new pads squeak. Also, a mechanical brake pad wear sensor cannot be installed on drum mechanisms, due to their design features.

Electrical

This is more modernand technological tools. They interact with the lamp on the instrument panel. The driver no longer has to listen to his car. All the necessary information is on the panel.

In turn, the electronic brake pad wear sensor is divided into two more subspecies:

• External devices.
• Integrated.

The first type is installed on the metal part of the block. On the side there is a special notch. The main plus is that when replacing the pads, the sensor does not need to be changed. It can be rearranged on a new brake element. Integrated devices are placed inside the friction lining. It is not possible to extract them. They are replaced as an assembly with new brake pads. It should be noted that these items are easier to replace.

Features of work

The electronic sensor consists of a metal core, which is placed in a plastic case. To eliminate the risk of damage to the brake disc (because the core will be in contact with it when you press the corresponding pedal), the rod is made of mild steel.

The operation of the brake pad wear sensor is based on contact closure. So, when the thickness of the pads is minimal, the electrical circuit will close. A corresponding light will appear on the instrument panel. Recently, manufacturers often install a two-signal brake pad wear sensor. So, the lamp can change its color infriction material wear.

Signs of problems

This item may fail for several reasons. The most common is damage or broken power wires. In this case, the lamp will not light up even when the pad wear is 99 percent. The second reason is the oxidation of contacts. This often happens at the junction of the sensor and the plug, near the caliper. During operation, water and dirt may come into contact with the sensor. All this affects the resistance of the circuit. As a result, the red light may come on even with new brake pads.

Also note that the eclectic sensor will retain its function even with wiring faults. The fact is that inside the element there is a steel core. When in contact with the disc, it will cause a characteristic sound. That is, the element will continue to operate, but only as a mechanical sensor.

How to replace?

Replacing the brake pad wear sensor can be done by yourself. To do this, you need to jack up the desired part of the car and unscrew the wheel. The external sensor will be located near the hub (we will not change the integrated one separately). The element is attached with a spring or with clamps. Carefully remove the mounting mechanism and take out the brake pad wear sensor itself. Next, you need to thoroughly clean the seat from dirt and deposits. The sensor contacts themselves are processed in the same way. Putting the new one in place of the old oneelement and fasten the wheel back. We lower the car from the jack. We check the performance of the new element. If the pads are worn, the lamp should be on. In some cases, to resume the correct operation of the sensor, it is enough to simply strip the contacts.

Regulations for changing pads

Many people are wondering after what period of time to change pads. Even the manufacturer will not give an exact answer to it, since it all depends on the driving style. Practice shows that with moderate use, the front pads "go" up to 40 thousand kilometers.

Rear ones last 2 times longer, because when braking, the main force is placed on the front. With an active driving style, the resource of friction materials will be up to 15 thousand kilometers. Experts do not recommend driving for a long time with the indicator lamp on. The steel tip wears out quickly, so, in addition to the pads, you will also have to change it.

Conclusion

So we figured out how the brake pad wear sensor works. As you can see, this is a very useful device that automatically signals the need to replace the friction linings. Such an element can often be seen on Mercedes and BMW cars. If desired, such a device is installed on other cars. The easiest way is to put a mechanical device. An electric sensor cannot be installed because there is no corresponding indicator lamp on the instrument panel.