Temperature sensor in the VAZ-2115: principle of operation, design and verification

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

Compliance with the thermal regime of the engine is one of the most important conditions for its long-term operation. To control the temperature on the VAZ-2115, like on any other car, there is a pointer and a corresponding sensor. The failure of one of them can ultimately lead to overheating of the power unit. Considering the importance of the temperature sensor in the VAZ-2115 for the trouble-free operation of the engine, knowledge of its structure, location and verification procedure will not be superfluous.

Design

The VAZ-2115 temperature sensor is a thermistor with a negative temperature coefficient. This means that its resistance decreases as the engine warms up. This is very convenient, because you can connect an ammeter in series, calibrated accordingly, and get the simplest temperature indicator withoutadditional conversions.

This is exactly the scheme used in the fifteenth model. In addition, the fluid temperature sensor in the VAZ-2115 is connected to an electronic control unit (ECU). Thus, the computer receives information about the thermal regime of the engine and makes adjustments to the composition of the working mixture. But that's not all. In the "tag", as in any car with an injection engine, there is no separate sensor for turning on the fan. It starts on a signal from the ECU in accordance with the data received from the DTOZH.

Where is DT located

Probably, for many it will be a revelation, but there are two temperature sensors in the VAZ-2115. One of them is installed on the thermostat and works in full cooperation with the on-board computer. The other is designed to operate a pointer device that shows the temperature. It is located at the end of the cylinder head, screwed into it horizontally. The sensors are similar in principle of operation, but differ in design. The one installed in the thermostat has two contacts for connection. For the instrument cluster sensor, the second connector is the vehicle ground.

Signs of malfunction

First of all, it should be noted that the damage listed below is typical mainly for an injection engine, where the temperature sensors in the VAZ-2115, in addition to the indication circuits, are also included in the power unit control system. So, you can determine the malfunction of the controller by the following signs:

1. No indication on the indicatortemperatures or their inconsistency with reality.
2. The fan does not turn on at the right time or does not work at all.
3. Rough idle. Among the many reasons may be a malfunction of the temperature sensor in the VAZ-2115.
4. Difficult to start the engine at low temperatures.
5. Coolant leaks from under the sensor housing.

For most symptoms, except for the most obvious ones, it is impossible to unequivocally diagnose a malfunction of the temperature controller. In any case, additional verification will be required.

How to make sure the sensor is working

First of all, consider the option when the temperature gauge on the instrument cluster does not work. Recall that the single-contact sensor screwed into the cylinder head is responsible for this. The check order is as follows:

1. Invite an assistant. No skill is required of him, his only task is to look at the instrument cluster.
2. Open the hood of the car and, observing all safety requirements, make sure that the connector that should be put on the sensor contact is in place.
3. If everything is fine, ask the assistant to turn on the ignition.
4. Remove the connector from the contact and briefly close it to ground.
5. If at this time the arrow of the device twitches to the right, it means that the coolant temperature sensor in the VAZ-2115 is definitely faulty.
6. If there is no reaction from the pointer device, the sensor is working. In this case, you should test the combinationappliances and check wiring.

If a sensor malfunction is diagnosed, then it can be eliminated only by replacing it with a new one, DTOZH cannot be repaired.

Two-contact sensor test

The responsibility placed on the controller does not allow it to be checked as easily as the previous one. The fact is that the correct operation of the engine directly depends on it. With its help, the optimal quality of the working mixture is selected and the fan is turned on, and this happens at a certain, predetermined temperature. Changing its parameters can lead not only to additional expenses, but also cause, albeit indirectly, the failure of the power unit.

Checking the two-contact temperature sensor of the VAZ-2115 engine is more painstaking and time-consuming. It is produced in the following sequence:

1. First you need to find the sensor, which is located on the pipe between the cylinder head and the thermostat.
2. For greater convenience and safety, it is necessary to dismantle the air filter and remove the terminals from the battery.
3. Drain coolant into a suitable container.
4. Disconnect connector from sensor.
5. Unscrew the sensor from the seat with a 19 spanner.
6. Take a liquid thermometer, multimeter and any device designed to heat water.
7. We fasten wires of suitable diameter and length to the sensor contacts. We fix their other ends on the probes of the multimeter.
8. Using the switch, set the limit on the device to 20com.
9. We lower the sensor into the water, the contacts must remain dry. We heat the liquid and monitor the readings of the thermometer and multimeter. They must match those given in the table.

Temperature (deg.)	20	40	60	80	100
Resistance (Ohm)	3520	1460	667	332	177

When taking measurements, you need to remember that the inertia of the thermometer is less than that of the temperature sensor, therefore, having reached the next control point, it is better to stop heating for a few seconds and wait for stable multimeter readings. In addition, the temperature values are given with great accuracy, but in reality this will not happen, a spread of 20-30 ohms is quite acceptable.

Conclusion

Despite the fact that checking the temperature sensor is not difficult, it is advisable to carry it out only in case of obvious signs indicating its malfunction. For any engine problems, more likely causes should be ruled out first and only the last to "suspect" DTOZH.