Checking the temperature sensor of the VAZ 2109

Each car engine is equipped with a device for measuring the temperature of the power unit. This component allows the driver to detect overheating in time and eliminate this problem. What is the fan switch on sensor on a VAZ 2109 with a carburetor engine, what is its structure and how to replace it - read on.

Coolant temperature sensor for VAZ 2109 and 21099 cars

First, it is advisable to know where the engine temperature sensor is located. On models 2108, 21099 and VAZ 2109, the coolant temperature sensor is installed between the cylinder head and the thermostat, in the exhaust pipe.

Device and principle of operation

The engine temperature controller itself is a thermistor-resistor device characterized by a negative temperature coefficient. The resistance parameter itself can be measured only when the temperature decreases or increases.

When the power unit heats up as a result of operation, the resistance indicator decreases; if the engine cools down, this parameter increases. For example, at the operating temperature of the engine on a VAZ 2109, the resistance is equal to 180 Ohms, and if it is 40 degrees cold outside, then the resistance will be equal to 100,700 Ohms. On one side of the DTOZH VAZ 2109 injector there are two contacts, and on the other there is a sensitive component, which is located directly in the flow of consumables.

As for the principle of operation, when the driver turns on the ignition, the control unit transmits voltage to the regulator via a resistor. Since the DTOZH itself is a thermistor, the voltage supplied from the control unit changes immediately taking into account the temperature of the consumable. When the parameter decreases, the unit analyzes the temperature and, in accordance with these data, determines the required volume of gasoline for injection. As the power unit warms up, the volume of gasoline that is transferred to the cylinders will decrease.

Two antifreeze temperature sensors for VAZ

In addition to starting, according to the readings of the regulator, the ECU adjusts the operation of the power unit at idle speed. As a result, he independently makes decisions on enriching the combustible mixture at high and medium loads on the internal combustion engine. This indicator can be changed depending on the ignition timing.

There are two temperature sensors on a carburetor car. One turns on the fan, the other is responsible for indicating the temperature on the dashboard.

Possible faults

There are several reasons why the regulator on the VAZ 21099 refuses to work.

So, why DTOZH does not work:

An electrical contact is located inside the device structure. Over time, this contact may simply break or cracks may form on it. If a break occurs inside the structure, this may cause complete failure. That is, the DTOZH will simply burn out. If there are cracks on the contact, the DTOZH, in principle, can work, but as a result of the lack of normal contact, the regulator will transmit incorrect data about antifreeze.
Poor device insulation. If the insulation is broken, short circuits may occur in the operation of the device. Accordingly, ultimately, these short circuits can lead to the DTOZH, again, burning out and having to be replaced.
There was a broken wire near the regulator. As a result of the break, the regulator will not be able to activate the fan designed to cool the power unit. Accordingly, this will lead to the engine overheating and may even boil (the author of the video is a Mechanical Technician).

How can a car owner understand that the DTOZh is out of order and it’s time to replace it?

To do this, it is enough to know about the main signs of problems, which we will discuss below:

The fan designed to cool the engine can turn on randomly at any time. In particular, the driver should be wary that the fan turns on when the engine is not completely warmed up. Remember that the fan should always function when the internal combustion engine is overheated.
The driver has difficulty starting a warmed-up internal combustion engine. The cooling system should automatically adjust the temperature, but because the unit is faulty, it cannot receive the correct signal.
If you carefully monitor the operation of the car, you will notice that gasoline consumption has increased. The increase in consumption is due to the fact that the car is simply overloaded when running on a hot internal combustion engine.
If the device fails completely, the gauge on the dashboard will show an incorrect temperature signal. A ten-minute drive is enough to warm up the engine. If after 10 minutes the temperature has not risen to the optimal temperature or when starting the internal combustion engine, the dashboard shows overheating, this indicates a malfunction.

Performance test

To check the thermal sensor, it will have to be removed from the car. To do this, follow these steps:

Allow the engine to cool to 40-50 °C to avoid burning your hands during operation. Partially or completely drain the antifreeze from the cooling system.
Disconnect the battery from the on-board power supply by removing the negative cable.
Disconnect the block with wires from the thermoelement.
Unscrew the part using a wrench of the appropriate size.

If the device is installed at the top point of the system, then it is not necessary to empty it entirely; it is enough to drain a third of the liquid into the container. All antifreeze must be drained when the thermocouple is located at the bottom of the radiator.

To carry out the tests you will need:

a multimeter or other device capable of measuring circuit resistance;
a small container for water (you can use a regular glass);
thermometer with a scale up to 100 °C.

A thermometer is essential if you want to make accurate resistance measurements by referring to the reference chart for your vehicle. When there is no table, the serviceability of the part is checked without a thermometer according to its operating principle: the hotter the water in the glass, the lower the resistance at the contacts should be.

Before checking the coolant temperature sensor under heating, test its contacts with an ohmmeter. It may happen that the device has burnt out or has a short circuit. Then further manipulations become meaningless and the element must be changed, since it cannot be repaired.

If the multimeter shows a certain resistance, then immerse the thermocouple in a glass of cold water and record the readings. Then add hot water and watch the resistance change, it should decrease. If there are no changes, purchase and install a new temperature sensor.

If the tests were successful and the device changes resistance when heating the water, then it is worth checking the connecting wires and cleaning the contacts. Little things like this often cause major problems.

Checking and replacing DTOZH

There are several options for diagnosing the device - the first one:

The negative probe from the voltmeter must be connected to the engine and turn on the ignition.
Using a tester, it is necessary to determine what voltage parameter is generated during movement.
If the DTOZH is working, then the voltage should be at least 12 volts when the battery is fully charged. If the obtained indicators are lower, it is necessary to replace or repair the device.

Temperature and Resistance Correspondence Table

Second diagnostic method:

You will need to set the multimeter to voltmeter mode - measurements are carried out in the range from 100 Ohms to 10 kOhms. Also prepare a thermometer that can measure temperatures greater than one hundred degrees. The regulator should be removed and placed in a container with antifreeze.
You need to warm up the coolant. As a result of an increase in temperature indicators, you need to monitor the readings given by the thermometer.
Using a multimeter, you should measure the resistance of the DTOZH at different temperature conditions. The obtained parameters should be compared with those indicated in the table above.

How to make the replacement yourself:

First of all, all the coolant must be drained from the radiator. Then disconnect the negative terminal from the battery, simply unscrew the nut with a wrench and disconnect it.
Next, you need to disconnect the block with wires that connects to the DTOZH.
Use a wrench to completely unscrew the device. Next, the regulator is removed from its seat; as mentioned above, this is the cylinder head exhaust hose. There is a rubber seal on the device itself; it cannot be lost when dismantling the DTOZH, especially if you have a new sensor without a seal.
Then install the new regulator in its seat, in the outlet hose. Using a wrench, tighten the adjuster all the way. After installation and tightening, the previously disconnected wiring harness should be connected to the DTOZH. The final step in this process is to pour the antifreeze back into the radiator and reinstall the disconnected negative battery terminal.

When to change?

If your car has a high signal level from the coolant temperature sensor, this may indicate a malfunction of the device. In the event of a breakdown, the device will need to be replaced. But before that, you need to know how to check the coolant temperature sensor; the symptoms of a malfunction are given below:

If the electronic regulator fails or does not work correctly, then the operation of the engine as a whole will be disrupted, in particular, it will be very difficult to start the engine in cold weather.
In the summer heat, the car engine already heats up to high temperatures. But if the DTOZH does not work correctly, then the engine will periodically lose “traction”, and over time, the malfunction can lead to increased gasoline consumption.
Another diagnostic option is to measure the resistance indicator. Resistance can be measured with a digital multimeter. To do this, you need to dismantle the device and place it in a glass with antifreeze, and you will also need a thermometer. The container needs to be heated, and then measure the required indicator using a digital multimeter. At a coolant temperature of 100 degrees, the resistance value will be about 177 Ohms. At 20 degrees this figure will be equal to 3520 Ohms.
If the DTOZH regularly shows overheating of the internal combustion engine of more than one hundred degrees, then check the condition of the antifreeze in the expansion tank. If everything is fine with the coolant and there are no signs of boiling, but the regulator continues to show too high a temperature, this may indicate a malfunction.

Video “Visual instructions for replacing the device”

You can learn how to replace the sensor yourself at home from the video below (the author of the video is Thoughts and advice from Mustafa Murtazaev).

The cooling system is responsible for the optimal temperature regime of the power plant, at which the power output is maximum. This system includes a radiator cooling jacket and pipes through which fluid circulates. Circulation is provided by a pump driven by the crankshaft.

Various types of coolant temperature sensors

The system also includes a thermostat, which ensures quick warm-up of the engine by shutting off the pipeline going to the radiator, while the liquid circulates only inside the cooling jacket. When a certain temperature is reached, the thermostat opens the pipe, after which the liquid circulates in a large circle, including the radiator.

The radiator cools the heated liquid. To cool the liquid faster, a fan is installed on the radiator, which creates additional air flow. But this fan does not always work; it turns on only when the liquid temperature exceeds a certain value.

Coolant temperature sensor

To monitor the coolant temperature, this system includes a coolant temperature sensor (CTS). The readings of this sensor are displayed on the dashboard, which provides the driver with information about the temperature conditions of the engine.

But this is not the main task of this sensor. The coolant temperature sensor transmits temperature data to the electronic control unit, after which this unit adjusts the fuel supply depending on the temperature. When the engine is cold, based on the readings of this sensor, the control unit sets an enriched mixture; after warming up, the fuel mixture becomes normal. Based on the readings of this element, the electronic unit regulates the ignition timing.

So the normal operation of the engine and fuel consumption largely depend on this sensor. It also drives the radiator fan. On some cars, a separate sensor is used to turn on the fan. It can be located either near the DTOZH or in the radiator.

General characteristics of the model

Dream car in the 90s

The dimensions of the car have changed somewhat due to the lengthening of the wing and enlargement of the hood. In addition, a completely new, improved VAZ radiator grille and, of course, an updated dashboard appeared. The length of the VAZ 21099 compared to other cars in this group has increased by 20 cm.

The VAZ 21099, like other models of this family, has many advantages:

it is capable of developing a fairly high speed;

has excellent controllability when driving;

Stable on completely different types of roads.

In 2004, this model of car was no longer produced in Russia, but its production continues in Ukraine.

VAZ 21099 cars come in two types.

The VAZ 21099 has a carburetor, just like the VAZ 21099 has an injector, the layout of the fuel supply system is almost identical.

In the VAZ 21099 injector, the supply of gasoline when you press the gas pedal is controlled by a computer. In a carburetor engine, such emissions are controlled by special damper plugs.

Quite often, the owners of this car are faced with one problem: the VAZ 21099 carburetor cooling fan does not work.

Signs of sensor malfunction

The temperature sensor is considered to be very reliable due to its comparative simplicity of design. However, there may be problems with it too. Usually they come down to a violation of the calibration, which leads to a violation of the resistance and, as a result, incorrect operation of the electronic unit, since it performs part of its functions based on the engine temperature.

One of the most obvious signs of DTOZ failure is the failure of the fan to turn on when the temperature exceeds the set value. But this indicator will not be reliable if there are two sensors - the main one, for transmitting the temperature value to the electronic unit, and the additional one, responsible for turning on the fan. In this case, failure to turn on the fan will indicate damage, oxidation of the wiring, or failure of the sensor responsible for its operation.

On modern cars, a malfunction indicating incorrect operation of the coolant temperature sensor is displayed on the display of the on-board computer. However, a fault message does not always indicate sensor failure. Often problems in its operation are associated with broken wiring or oxidation of contacts.

Incorrect functioning of the coolant temperature sensor or a break in its wiring leads to excessive fuel consumption, high idle speed, and detonation. It is possible that the power unit will have difficulty starting after warming up. The biggest trouble that can occur due to the inoperability of this sensor is overheating of the power plant, which can cause the cylinder head to move.

How to check without removing it from the car

If you suspect a faulty DTOZH, it is not necessary to remove it from the car. All manipulations can be done without dismantling using a tester or diagnostic device. Let's consider each of the methods in more detail.

Pre-check

To check the temperature meter, start the car and let the engine warm up at idle to 90 - 95 0 C.

Disconnect the connector from the sensor and notice how the arrow on the instrument panel behaves:

Sensor check

Diagnosing the performance of the DTOZH is not difficult. But before you do it, it is advisable to check the integrity of the wiring going to it. You can also check the voltage coming from the control unit. To do this, you need to disconnect the chip with wires from the sensor and connect it to a voltmeter. After this, start the engine and measure the voltage supplied to the sensor; it should correspond to 5 V.

To remove, diagnose and replace the temperature sensor you will not need much:

Key to 19;
Multimeter;
Container for draining coolant;
Electric kettle;
Thermometer;

Before removing the element, you need to partially drain the liquid from the system. It is not necessary to drain it all, since it is located at the top of the engine; it is enough to drain it to a level below the DTOZH position.

Then the chip with wiring is disconnected from the sensor. Using the 19 key, it turns out of its seat.

Video: Checking the coolant temperature sensor

Something else useful for you:

Check the sensor using an electric kettle with a thermometer and a multimeter set to resistance measurement mode. There are two ways to carry out diagnostics.

In the first method, the working part of the DTOZH is immersed in an electric kettle with cold water, and a thermometer is also placed there. You can only use an electronic thermometer that can measure high temperatures. A multimeter is connected to the sensor itself and the electric kettle is connected to the network. As the water temperature rises, the sensor resistance will drop. So, at a water temperature of +15 C, the resistance should be 4450 Ohms. At +40 C, the multimeter reading should be 1459 Ohms. The water needs to be heated to a temperature of 100 C. At this value, the resistance should be minimal - 177 Ohms. If the values differ, it means that the sensor is providing incorrect information.
The second method is suitable if you do not have a thermometer. To measure the resistance, the DTOZH is immersed in water after it has boiled. In this case, the water temperature will approach 100 C. This is quite enough for taking measurements. After lowering the working part of the temperature sensor into boiling water, the resistance should be slightly more than 177 Ohms. If the difference is large, the sensor is faulty.

Fan diagnostics

In order to check the operation of the unit, you will need a one and a half meter wire, preferably with “crocodiles” at the ends. With the engine off, connect a wire from the plus terminal of the battery to the fan contact directly. A working unit should begin to rotate. If it doesn't start, it's faulty. If the cooling fan does not turn on when the engine overheats, although diagnostics indicate that they are working properly, you should check the DTOZH.

When testing, you will need an ohmmeter to measure the resistance of the sensor. An ohmmeter is included in any, even the simplest portable digital multimeter. The procedure is as follows:

With the cold engine turned off, remove the wires from the DTOZh contacts.
Set the multimeter mode switch to the “resistance measurement” position.
Measure the sensor resistance. At room temperature it should be approximately 2,200 - 2,800 ohms.
Reinstall the sensor wires.
Start the engine and let it warm up at idle speed to about 80 degrees.
Turn off the engine. Remove the wires from the sensor contacts.
Measure the sensor resistance. At 80 degrees, the resistance should be in the range of 270 - 389 Ohms.

If for some reason the sensor resistance does not meet the standard, the part must be changed. And if it does, but the unit does not turn on, something is not working in the electronic engine control unit. This should be addressed to a service station. To diagnose and flash the ECU, you need special equipment.

The VAZ 21099 sedan is the final model of the Samara series. It was manufactured on the basis of the VAZ 2109; it was slightly different from other variants of this family by the front end of the body.