Oil level sensor: device, principle of operation, types, diagrams
Auto Terms,  Car device

Oil level sensor: device, principle of operation, types, diagrams

Every car ICE needs high-quality cooling and lubrication. For this, cars with 4-stroke engines have a lubrication system in which engine oil is poured. There are two types of them: dry sump or wet sump. A similar system is used if the unit is a valve or 4-stroke (for the differences between such a modification and a two-stroke, read here).

More details about the types of lubrication systems are described in another review... Over time, the engine oil in the system becomes less, which is why, at a level below the minimum, the power unit begins to experience oil starvation, and in some cases, the electronics muffles the internal combustion engine and does not allow it to start.

To check the lubrication level, the driver periodically uses a dipstick, on which the manufacturer indicates the minimum and maximum values. The oil should be between these marks. However, many modern vehicles do not provide for such a check - there is no dipstick in the motor at all.

Oil level sensor: device, principle of operation, types, diagrams

Instead of a conventional dipstick, the injector will be equipped with an electronic equalizer. In this case, the electronic control unit controls the operation of the engine and notifies the driver of any malfunctions, including the state of the lubrication system of the unit.

In such cars, the dashboard has a separate indicator that signals an imbalance in the oil level. This indicator is triggered by the indicators of the oil sensor. Let's take a closer look at the device, the principle of operation and the types of quiet sensors.

What is a car oil level sensor

The word sensor itself indicates that it is an electrical sensor that allows you to determine how much oil is in the engine reservoir (sump). Depending on the design, the device will have an individual wiring diagram.

An engine equipped with an oil level sensor will have a corresponding hole in the lower part of the crankcase, in which this device will be installed. In most cases, it will be between the filter and the pan. In addition to the engine, the gearbox can also receive a similar sensor. A sensor with a similar operating principle can be equipped with an electric generator or other mechanical device that uses a 4-stroke internal combustion engine.

Устройство

The oil sensor can have a different device depending on the principle of operation and additional functions that it can perform. Most modern devices are of an electronic type. Their connection also depends on the principle on which they will work.

Oil level sensor: device, principle of operation, types, diagrams

The simplest sensor is connected from the on-board power supply. When it is triggered, the contact of the light is closed, which will indicate that it is necessary to replenish the level in the pallet. As for electronic modifications, their principle of operation is reduced to the activation of the corresponding algorithms programmed in the microprocessor.

When the device is triggered, corresponding signals are generated in the electrical circuit. They go to the control unit. The ECU determines which signal needs to be output to the tidy. In some vehicles, an acoustic signal or graphic is activated in conjunction with a lighted indicator.

The photo shows a simple cross-section of a sensor:

Oil level sensor: device, principle of operation, types, diagrams
A) minimum oil level; B) maximum oil level; 1) magnetic contact; 2) a float with a magnet; 3) body; 4) connector for wiring.

The device of the simplest sensor (float type) includes the following elements:

  • Magnetic contact (reed switch)... This element reacts to the movement of the magnetic float. When the magnet is in the field of action of the contact, the circuit is closed and the signal on the dashboard lights up.
  • Float... This element is located on top of the body. When the sensor is in a liquid, the dense medium displaces the float and is constantly on top of the oil. The float contains a permanent magnet. A change in the level in the tank causes the float to move. When it drops to the minimum value, the reed switch contact closes.
  • Chassis... This is a long hollow tube, inside which is the reed switch itself and its electrical component (insulated metal thin rods with a break contact). Outside the body, a float with a magnet, made in the form of a ring, moves.
  • Electrical connector... In the simplest circuit, the sensor is powered by a battery, and a signal light is connected in series to it.

This design can be used not only in oil tanks. A gas tank or cooling system can receive a similar sensor. In most cases, the device is installed using a threaded connection (screwed into the tank itself: engine block, fuel tank, gearbox housing, etc.).

How does the oil level sensor work?

The simplest operating principle has a float type sensors. When the level of lubricant or other monitored liquid drops, the circuit closes (in some cases, it opens on the contrary) and an alarm is triggered.

Calibration of the device should not be carried out on a cold engine. At this point, the oil level will generally be at maximum or within acceptable limits. When the engine starts, some of the grease will surely go away.

Oil level sensor: device, principle of operation, types, diagrams
In this modification, the reed switch contact closes at the maximum level, and at the minimum it opens

When the ignition is activated, the electrical circuit is closed, and the corresponding signal is sent to the relay. Due to the fact that the float is constantly on top, there is an uninterrupted level control. As soon as the liquid is produced, or there is a leak, the float gradually lowers and the magnet stops acting on the reed switch contacts (or vice versa, closes the contact). The circuit is closed / opened. The relay reacts to the absence or power supply and closes the signal lamp circuit.

As mentioned earlier, modern cars are equipped with more complex sensors, which are no longer mechanical, but electronic. Depending on the version, these devices can perform other functions, not just oil level monitoring.

In a simple design, the sensor only activates the signal lamp. At the same time, the driver does not receive up-to-date information: he only finds out when the level has dropped to a minimum. More advanced sensors allow you to check the quality of the oil, its pressure and temperature. Depending on the signals received from the sensor, a special message may be displayed on the dashboard.

Here is a small display table in some cars:

Icon:Signal:The reasons:How to fix:
Yellow oil can
Oil level sensor: device, principle of operation, types, diagrams
Glows constantlyOil level dropped to minimumThe engine turns off, if there is a dipstick, then the lubricant level is checked. In the absence of a dipstick, add a little oil to the filler neck and go to the service station, if the signal does not disappear
Exclamation point with scale and arrow (or red oiler)
Oil level sensor: device, principle of operation, types, diagrams
Glows constantlyOil pressure does not match the programmed parameterImmediately go to the service station. In the process of movement, do not bring the internal combustion engine to high revs.
Red buttercup
Oil level sensor: device, principle of operation, types, diagrams
BlinkingToo low pressure in the lubrication systemStop the engine immediately and measure the lubricant level in the engine (if equipped with a dipstick). If, when the level is replenished, the light continues to flash, call a tow truck and tow the car for service
Yellow oil can
Oil level sensor: device, principle of operation, types, diagrams
BlinkingA malfunction has occurred in the engine lubrication system, for example, the sensor is faultyContact a car service. Replace sensor.

On some car models, there is a tidy with a graphical display of oil level parameters. In this case, you need to see what value each character has. Typically the two center symbols will indicate normal and below average. The upper and lower symbols indicate, respectively, the maximum and minimum values ​​are exceeded.

Oil level sensor functions

Depending on the design, modification and electrical circuit of the device, the sensor can measure not only the level of the lubricating fluid. So, a car from the BMW model range can be equipped with a level and condition sensor for engine lubricant. In addition to monitoring the amount of oil, this device allows you to determine when it needs to be changed.

Oil level sensor: device, principle of operation, types, diagrams

Many modern cars signal the need for maintenance of the lubrication system based on mileage, but this is not always an accurate definition. The reason is that the car can drive 15 thousand on the highway, but the oil will still be suitable for operation, since the engine runs stably without overloads.

On the other hand, a car operating in a megalopolis is often in traffic jams and tidbits. Such transport may not pass the prescribed mileage, and the oil will already need to be replaced, since the engine is running, and the car does not move much. This concept is called engine hours. This term is described in detail. in another article.

Sensors that monitor the condition of the oil, if the indicator does not match, will issue an alarm that will be displayed on the dashboard. Some modifications are also capable of measuring the pressure in the engine lubrication system, which will also be indicated on the tidy with a luminous oiler.

Oil level sensor: device, principle of operation, types, diagrams

Another function that some oil sensors have is to measure the temperature of the lubricating fluid. These devices are often used in dry sump systems. They use an individual radiator to cool the oil to the required temperature.

Sensor classification

If we divide all oil sensors into main categories according to security, then there will be three of them: waterproof, dustproof, explosion-proof. As for the classification by mechanical resistance, all devices are divided into vibration-resistant and vibration-resistant types.

In mechanisms equipped with an internal combustion engine, be it a car, a walk-behind tractor or a gas generator, sensors of the following type can be used:

  1. Float;
  2. Temperature;
  3. Ultrasonic.

Each of the listed modifications has an individual device and scheme of work. The location of these devices is basically the same - in the upper part of the sump, but there are also options installed near the oil filter. Let's consider each of these varieties separately.

More about the float sensor

This type is the simplest not only in the device, but also in the principle of operation. Its design was reviewed a little earlier. The float is loosely attached to the vertical tube in which the reed switch is located. In this case, the oil will drive this element up / down, due to which the magnetically controlled contact either closes or opens.

In most modifications, the device works as follows. As long as the float is at a sufficient level from the sensor contact, the circuit is open. As soon as the amount of oil becomes small, the magnet descends and begins to act on the contact, closing the electrical circuit. The control unit detects this signal and activates the watering can on the tidy.

Oil level sensor: device, principle of operation, types, diagrams
A) is installed on a vertical surface; B) is installed on a horizontal surface.

The advantage of a mechanical sensor is that it rarely fails. This happens if the tightness of the tube is broken, when the magnet loses its properties (demagnetized), a wire break or breakage of the magnetically controlled contact occurs. The main cause of most breakdowns is motor vibration.

Float sensors also have several significant disadvantages. Firstly, they do not show the real amount of oil, but only turn on when the level drops to a critical value. Secondly, deposits from old oil can accumulate on the surface of the tube, which can impede the movement of the float.

A similar problem can occur with the float itself. Due to the large amount of deposits, the float may not be on the surface of the measured medium, but slightly immersed in it, which also distorts the measurements. In this case, the lamp may light up even if the lubricant level is acceptable.

Some car owners without such sensors upgrade their vehicles by installing a homemade equalizer. In fact, it will be a device assembled from models for other cars. To install a homemade sensor, you need to make a corresponding hole in the pallet, weld a nut with a suitable thread in this place and install the device from another car.

True, in order for the sensor to show the real critical level, you need to adjust the maximum and minimum float heights.

More about heat sensors

This modification has a more complex structure. Such sensors simultaneously perform two functions at once: they measure the level and temperature of the lubricant. They are in great demand, as they are easy to manufacture and work reliably for a long time. The device includes a wire and a heating element, enclosed in a housing.

Thermal sensors will work according to the following principle. When the driver's hand activates the ignition (turns the key in the ignition lock), voltage is applied to the wire. She heats up. The oil in which this element is located begins to cool it. The ECU reacts to the cooling rate and determines the oil level based on this (the faster the cooling, the more oil in the reservoir). The entire process (heating and cooling) takes place in milliseconds.

Oil level sensor: device, principle of operation, types, diagrams

In the category of temperature sensors for oil level, there is also an electrothermal counterpart. They are almost identical in design to conventional sensors. They work according to the same principle: heating and cooling the wire in oil.

An exception is the way of calculation. The device has a sensitive element, the resistance of which determines the level of the liquid in the sump. So, the more oil in the tank, the deeper the sensor will be in it, and its resistance will be lower.

Such modifications fail not only with the wear of the main components, but also with the appearance of difficulties with heating the wire, the formation of corrosion on the sensitive element and the layering of oil deposits on it. These devices are not repaired - only they are replaced. Due to the low cost of production, the price of such a sensor will not be too high.

Such types of testers are in demand due to the simplicity of their design and the ability to record various changes in the volume of oil. The device more effectively determines the permissible and minimum amount of lubrication compared to the previous modification.

More about ultrasonic sensors

In modern automotive industry, wireless technology is gaining popularity: steering without physical connection with the rail, accelerator and brake pedal without cables and wires, etc.

Ultrasonic sensors also work without close contact with the lubricant. They do not need to be immersed in oil. Thanks to this, grease leakage is excluded if the gasket is leaking or the mechanic has not screwed the device in the crankcase poorly (if the device is installed close to the maximum lubricant level).

The device works according to the following scheme. The sensor is installed at the top of the tank (the sensor is not immersed in oil). When the driver activates the ignition, the device begins to emit ultrasonic waves. The signal is reflected from the surface of the lubricating fluid and is sent to the sensor receiver.

Oil level sensor: device, principle of operation, types, diagrams

The device records the time interval between the pulse itself and the signal reflection. This time is analyzed by the control unit (it is stitched for a specific time frame), on the basis of which the level in the sump is determined (how much free space between the receiver and the oil surface). This type of sensor is used in machines with a graphical display of the amount of oil in the system. In addition to measuring the amount of lubricant, most of these devices are able to determine its temperature.

Since only electronics take part in the measurement, it allows you to more accurately record critical values ​​in different modes of motor operation. For example, in a cold engine, the electronics can determine the oil level as critically high, but after a couple of minutes of operation of the unit, the amount of lubricant decreases sharply.

This can be interpreted as oil loss. But in the control unit, based on the data it receives from other sensors, an algorithm is activated, indicating that such abrupt changes are normal.

Some motorists modernize the lubrication system of their cars by installing a wireless device instead of the standard sensor (a plug is placed in its place). In this case, it is necessary to do some modernization of both the lubrication system itself and the operation of the control unit. The cost of such a procedure can be prohibitive compared to the efficiency and convenience of using such a sensor. In addition, it may not be suitable for a specific vehicle.

Oil level sensor malfunctions

Damage to the oil level sensor cannot be ignored. If the driver misses the moment when the lubricant level drops to a critical minimum value, the engine will experience oil starvation. In addition to its lubricating effect, engine oil also removes heat from parts of the unit that are not in contact with the cooling jacket.

If there is not enough lubrication, the load on the motor increases, especially thermal (parts are poorly cooled). This negatively affects their working life. In life, the feedback of many car owners shows that even the minimum level of lubrication can be uncritical if the internal combustion engine is not brought to high speeds until the oil is changed or until an additional portion of lubricant is added.

Oil level sensor: device, principle of operation, types, diagrams

A permanently lit oil can lamp on the dashboard indicates a breakdown of the sensor. If the alarm persists after topping up or completely changing the oil, then the sensor must be replaced. This can also happen when the ECU receives incorrect signals.

In addition to a constantly burning light on the tidy, the motor icon may light up or the oiler periodically lights up and goes out sharply. In this case, the control unit receives incorrect data from the lubricant level sensor. The microprocessor detects this as a serious malfunction, and may even block the operation of the motor.

If the car does not have a dipstick for checking the oil in the engine, then apart from diagnostics at the service station, the breakdown cannot be determined in any way. Service center workers connect a car scanner and diagnose all equipment. In addition to this method, in the case of some vehicles, a quick self-diagnosis is possible.

An error code is displayed on the vehicle's on-board computer. In most cases, the P250E error indicates a malfunction of such a sensor (but often this refers to deep diagnostics, which is carried out by a special autoscanner). For details on how to call up the diagnostic menu on the on-board computer of the car, it is described in another review.

Oil level sensor: device, principle of operation, types, diagrams

The oil level sensor stops working for the following reasons:

  • A large amount of oil deposits have accumulated on the surface of the scanning device;
  • Violation of the insulation of the wiring or a break in the line;
  • Blown fuse (pinout will help to find the corresponding element in the fuse box, which is mainly indicated on the case cover);
  • For VAG models, sensor malfunctions are directly related to the breakdown of the hood end switch.

It would seem, what does the hood have to do with the oil level sensor. Manufacturer logic (applies to cars coming off the assembly lines of companies, belonging to the VAG concern) is next. The electronic circuit is looped through the hood limit switch. When the driver noticed that the oil can lit up on the tidy, naturally, he will open the hood to add oil, or at least check its level.

The triggering of this sensor gives a signal to the control unit, they say, the driver made the necessary changes and went to the service station. Counting on such a course of action, the manufacturer programmed the ECU to turn off the alarm on the tidy until the car has traveled about 100 kilometers (if the oil was not topped up).

Oil level sensor: device, principle of operation, types, diagrams

Limit switch malfunctions are regarded as a breakdown of the oil sensor. For this reason, before installing a new sensor in such machines, you must first check the serviceability of the limit switch. Otherwise, even a working sensor for the lubrication system will not cause the oiler on the dashboard to go out.

Selecting a new sensor

The choice of a new device today is quite simple due to the fact that different manufacturers produce a large number of all kinds of auto parts for different models. Thanks to this, the range of sensors, including those for measuring the level, temperature and pressure of oil in the engine, is huge.

It is better to install a device that was created specifically for a specific car model, and not to select analogues. The most reliable way to find the appropriate equalizer is to search for the vehicle's VIN number. About where this code is located and how it is deciphered, it is described here... The reason is that the car may belong to a restyled series of a separate generation (for how restyling differs from a facelift and the release of the next generation, read separately), which is why the technical part of the same model, but different year of manufacture, may differ.

The second way to find a device is by the catalog number or the number indicated on the device itself. You can also find an original spare part by telling the seller the model of the car, the volume of the engine (what is the difference between the total and working volume of the internal combustion engine, read here) and when the car came off the assembly line.

If there is a desire to install a modern ultrasonic instead of the standard thermal or float type, then first you need to consult a professional about this possibility. You should not install a homemade version, as it may not work correctly or conflict with the car electronics.

Oil level sensor: device, principle of operation, types, diagrams

Ideally, you should come to the service center with an original spare part or search for an option from the company's catalog if the car service offers a similar service. If it is not possible to purchase an original equalizer, then you can choose a budget analogue that is not inferior in quality to the original.

Such products are offered by the following companies:

  • German Hella, Metzger, SKV or Hans Pries;
  • Italian ERA or Meat & Doria;
  • Japanese Denso.

Most mechanical (float) and thermal sensors are universal and can be installed on different vehicles. As for the cost, the original will cost about 50-60 percent more than the budget analogue, although the quality may not exceed it.

Hack and predictor Aviator

So, monitoring the condition of the oil in the engine lubrication system in modern cars is no longer an additional option, but an integral function. An electronic leveling gauge makes it easy to check the level, temperature, pressure, and in some modifications, the quality of the oil in the crankcase.

The malfunction of this sensor is quite rare, but if necessary and desired to tinker around the car, it changes easily without the use of additional equipment. The main thing is to make sure that this particular element is faulty.

This video, using the VAZ 2110 as an example, shows where you can find this equalizer and how to replace it:

Oil level sensor in the VAZ 2110 engine: what is it, where is it and how to replace it!

Questions and answers:

How does the engine oil level sensor work? This sensor works on the principle of a sonar (ultrasound is reflected from the surface of the oil and is received by the device). The oil level is determined by the rate at which the signal is received.

What is the name of the oil level sensor? Radio technicians call the oil gauge element a reed switch. A permanent magnet works with it. Depending on the oil level, the magnet acts on the reed switch (in float switches).

Where is the oil level sensor located? Since this sensor must detect the amount of oil, it must interact with the lubricant in the machine. Therefore, it is installed in an oil reservoir.

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