A sharp increase in force on the steering wheel when parking or the appearance of an extraneous hum in the front suspension most often indicates the beginning of destructive processes inside the mechanism steering rack. Unlike hydraulic analogues, where the pressure is created by a pump, here an electric motor integrated into the housing or mounted on the shaft is responsible for creating the force, which requires a detailed understanding of the electrical and mechanical parts of the assembly for correct diagnosis. Lack of fluid ATF in the system does not mean complete reliability, since mechanical wear of the gear pair and shaft bearings occurs regardless of the type of amplifier drive.
Structurally modern electromechanical power steering (EPS) is a complex unit that combines precision mechanics and high-precision electronics. Understanding exactly how gears, shafts and torque sensors interact allows the car owner to distinguish a real component failure from a software error or a low battery. Ignoring primary symptoms, such as biting in extreme positions, can lead to complete failure of the control system and loss of control over the trajectory of movement.
⚠️ Attention: Attempting to open the case yourself EUR without special tools and calibration equipment will often result in permanent damage to the ring gear or reset of the position sensor, making further operation impossible.
Schematic diagram of the operation of an electromechanical amplifier
Fundamentally steering rack device with electric drive is based on the conversion of the rotational movement of the steering wheel shaft into the translational movement of rods, but with the significant addition of electric traction. The key element here is the torque sensor, which detects the slightest force applied by the driver to the steering wheel and transmits a signal to the electronic control unit (ECU). Based on the data received, the controller calculates the required force and direction of current for the electric motor, which adds force to the main shaft through a belt drive or worm mechanism.
Unlike the hydraulic booster, which works constantly and creates a load on the internal combustion engine, the electric motor turns on only when the wheels are turning. This provides significant fuel savings and eliminates the need to regularly replace hydraulic fluid and belts. Electronics also allows you to flexibly adjust the steering force depending on the speed of the car: at low speeds the steering wheel becomes very light, and on the highway it becomes heavier and more informative.
Differences in electric motor layouts
There are three main options for integrating the motor into the device: on the steering column shaft, on the input shaft of the rack, or directly on the gear sector of the rack itself. The latter option is considered the most effective, as it provides the best feeling of the road and minimizes inertial losses.
To extend the service life of the electric power steering, avoid holding the steering wheel in the extreme position for more than 5 seconds, as this causes overheating of the electric motor and a surge in current in the windings.
Main structural units and their purpose
The central element of the entire system is the housing, inside which the gear shaft moves. This shaft is directly connected to the steering wheel and has a toothed sector at the end that interacts with the rack. It is the gear transmission rack and pinion provides the main mechanical advantage and transmission of force to the steering knuckles. In devices with electric power steering, this unit is often made more compact, since part of the load is taken on by the electric drive.
The electric motor, which is the heart of the amplifier, can be brushed or brushless. In modern cars they are increasingly used brushless motors due to their durability, lack of sparking and ability to precisely control torque. The engine is connected to the rack shaft either through gears or through a belt drive, which also serves as a damper that dampens vibrations from the road surface.
- 🔧 Steering angle sensor - reads the position of the steering wheel for the operation of stabilization systems.
- ⚙️ Torsion bar is an elastic element, the twisting of which is recorded by a torque sensor.
- 🔌 Control unit (ECU) - processes sensor signals and controls the supply of current to the motor.
An important component is also the backlash compensation mechanism, which is often represented by a spring-loaded nut or similar device. This element presses the rack against the pinion, allowing clearance without creating excessive friction. B electrical racks the adjustment of this unit is critical, since backlash can cause false signals to the control system.
Electronic control system and sensors
Intellectual component EUR consists of a complex system of sensors that continuously monitor the condition of the vehicle. The main sensor is a torque sensor located on the input shaft torsion bar. It measures the resistance to turning the steering wheel: the harder the driver presses on the steering wheel, the more the torsion bar twists and the more powerful the signal is sent to the amplifier. In parallel with this, the control unit reads data on vehicle speed, engine speed and wheel steering angle.
Data processing occurs in real time with a high sampling rate. If the system detects a sudden jerk in the steering wheel or the start of a skid, electronic unit can adjust the force or even independently twist the wheels to stabilize the trajectory (active return to zero function). The reliability of the entire system directly depends on the quality of the contacts and the condition of the wiring, since any interference in the signal lines can lead to an emergency shutdown of the amplifier.
| Component | Function | Typical fault |
|---|---|---|
| Torque sensor | Steering force measurement | Signal break, track wear |
| Electric motor | Creating Extra Force | Brush wear, winding breakage |
| Control unit | Data processing and management | Burning power switches |
| Torsion bar | Torque transmission | Slipping, breaking |
Typical mechanical faults
Despite the lack of hydraulics, the mechanical part steering rack subject to wear. The most common problem is wear in the gear-rack gear pair. This leads to play, which is felt as free movement of the steering wheel in the center position or a wobble in the steering wheel when driving on uneven roads. In some cases, wear is compensated by tightening the adjusting screw, but in deep mining, replacement of the unit is required.
Another vulnerable point is the bearings and sliding bushings in which the shaft moves. When the protective boots are destroyed, abrasive dust and moisture enter the mechanism, which accelerates corrosion and wear of rubbing surfaces. Rack shaft corrosion is one of the most dangerous malfunctions, since rust destroys oil seals and cuffs, and can also cause the mechanism to bite while in motion.
⚠️ Attention: The appearance of a knock when driving over uneven surfaces is often ignored by owners, but it is this symptom that indicates the beginning of wear of plastic bushings or the appearance of play in the rod joints.
A common problem is wear of the drive belt (if it is provided for in the design) or gears of the gearbox. Belt stretching reduces the efficiency of power transmission from the motor to the shaft, which manifests itself as a “wobbly” steering wheel or a delayed response of the amplifier. In rare cases, the rack body itself breaks down due to strong shock loads, for example, when a wheel hits a deep hatch at high speed.
Diagnosis of electrical faults
Diagnostics EUR begins with a visual inspection and checking the voltage in the on-board network. Low battery voltage or a faulty alternator can cause the amplifier to shut down, as the system perceives this as an emergency. At the same time, the steering malfunction indicator light on the dashboard lights up, and the steering wheel becomes heavy. The first step should always be computer diagnostics with a scanner that reads error codes from the control unit's memory.
Errors may indicate an open circuit in the motor, a faulty torque sensor, or overheating of the system. It is important to distinguish between software failures and hardware failures. Sometimes resetting errors helps to temporarily restore functionality, but if the problem lies in physical damage to the wiring or burnt-out transistors in the control unit, repairs are inevitable. Particular attention should be paid to the places of the harnesses passing near the moving parts of the suspension, where insulation chafing is possible.
☑️ Primary diagnosis of EUR
Comparison with hydraulic booster and unit resource
The main advantage electric booster In front of the hydraulic booster is energy efficiency and the absence of the need for regular maintenance of the liquid system. There is no need to change the fluid, monitor the level, replace pump belts or worry about seal leaks under high pressure. The service life of modern electric racks during normal operation often exceeds 200-250 thousand kilometers, which is comparable to or higher than the service life of hydraulic analogues.
However, there are also disadvantages. Electrical systems are more sensitive to overheating when operating at low speeds for long periods of time (for example, when parking in cold weather). In such conditions, the hydraulic booster simply circulates fluid, cooling, while the electric motor can go into thermal protection, temporarily turning off. In addition, electrical repairs often require expensive, specialized equipment and skilled electrical engineers.
- 📉 The absence of hydraulic fluid simplifies the design and is environmentally friendly.
- 🔋 Independence from the operation of the internal combustion engine.
- 🛠️ Fewer rubbing parts in the pump drive (there are simply none).
The influence of temperature on the operation of the EUR
In severe frosts, the lubricant in the mechanical part thickens, which increases the load on the motor. The control unit can artificially limit the maximum current until the unit warms up, so in the first minutes of driving the steering wheel may seem tight.
Recommendations for operation and maintenance
To ensure maximum resource steering rack with EUR You must follow a few simple rules. First of all, you should avoid sharp impacts with the steering wheel on curbs and obstacles, since the mechanical strength of the gear pair is limited. It is also important to monitor the condition of the rod boots: any microcrack allows water and dirt to penetrate inside, causing accelerated corrosion of the shaft.
If the first signs of a malfunction appear, such as extraneous sounds, jerking or the error lamp lights up, you should not postpone a visit to the service center. Operating a car with a faulty amplifier is not only uncomfortable, but also dangerous, since in an emergency the driver may not be able to control the car. Regular computer diagnostics allows you to identify problems at an early stage, before they lead to expensive repairs or replacement of the assembly.
Timely replacement of damaged linkage boots is the cheapest and most effective way to extend the life of an expensive electric power steering rack.
Is it possible to adjust the rack tension yourself?
In theory, an adjustment screw is available, but proper adjustment requires a special torque tool and an understanding of preload torque. Incorrect adjustment will lead either to knocking or to the rack biting and its rapid failure.
Why did the EUR error light come on after washing?
Water could get into the sensor connectors or onto the electric motor contacts, causing a short circuit or distortion of the signals. It is necessary to dry the engine compartment and reset the error. If the problem recurs, troubleshooting of the connectors is required.
Frequently asked questions (FAQ)
How long does an electric power steering rack last?
The average resource of a high-quality unit is from 150,000 to 250,000 km. However, this indicator greatly depends on operating conditions, road quality and the condition of the vehicle’s suspension. With careful driving, the rack can last longer.
Is it possible to drive if the electric power steering is turned off?
Yes, the car will retain controllability, since the mechanical connection between the steering wheel and the wheels remains. However, the steering wheel will become very heavy, especially at low speeds and when parking, which requires significant physical effort from the driver.
Do I need to change the fluid in the electric power steering?
No, there is no working fluid in a classic electromechanical power steering. There may be a conservation lubricant inside the mechanism, which usually does not require replacement during the entire service life of the unit, unless repairs have been made.
Why does the steering rack with ESD hum?
A hum can be produced by an electric motor when bearings or brushes are worn, as well as by the mechanical part itself when there is a lack of lubrication or the presence of backlash. Often the sound is transmitted through the body and can be mistaken for the hum of a pump, which is not in this system.
⚠️ Attention: Ignoring the illuminated steering fault lamp may lead to sudden failure of the power steering, which creates an emergency situation on the road.