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 an arrow pointer and a corresponding sensor. The failure of one of them can ultimately lead to overheating of the power unit. Given 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 temperature sensor VAZ-2115 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 in series an ammeter, calibrated accordingly, and get a simple temperature indicator without additional conversions.
It is such a scheme that is used in the fifteenth model. In addition, the liquid 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 is not all. In the "tag", as in any car with an injection engine, there is no separate sensor for turning on the fan. It is triggered by a signal from the computer 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 a thermostat and works in full cooperation with the on-board computer. Another is designed for the operation of a dial gauge showing temperature. It is located at the end of the cylinder head, screwed into it horizontally. The sensors are similar in principle, but differ in design. The one installed in the thermostat has two contacts for connection. In the instrument cluster sensor, the second connector is the vehicle ground.
Symptoms
First of all, it should be noted that the damage listed below is typical mainly for an injection engine, where temperature sensors in the VAZ-2115, in addition to indication circuits, are also included in the powertrain control system. So, you can determine the malfunction of the controller by the following symptoms:
- Lack of readings on the temperature indicator or their inconsistency.
- The fan does not turn on at the right time or does not work at all.
- Unstable idling. Among the many reasons there may be a malfunction of the temperature sensor in the VAZ-2115.
- It is difficult to start the engine at low temperatures.
- Leaks of coolant from under the sensor housing.
For most symptoms, besides the most obvious, it is not possible to unambiguously diagnose a malfunction in the temperature controller. In any case, additional verification is 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 one-contact sensor screwed into the cylinder head is responsible for this. The verification procedure is as follows:
- Invite an assistant. No dexterity is required from him, his only task is to look at the instrument cluster.
- Open the hood of the car and, observing all safety requirements, make sure that the connector that must be worn on the sensor contact is in place.
- If everything is fine, we ask the assistant to turn on the ignition.
- We remove the connector from the contact and briefly close it to ground.
- If at this time the arrow of the device jerks to the right, it means that the coolant temperature sensor in the VAZ-2115 is definitely faulty.
- If there is no reaction from the side of the dial gauge, the sensor is working. In this case, test the instrument cluster and check the wiring.
If a sensor malfunction is diagnosed, then it can be eliminated only by replacing it with a new one, and DTOZH cannot be repaired.
Testing a two-pin sensor
The responsibility assigned to the controller does not allow it to be verified as easily as the previous one. The fact is that the correct operation of the engine directly depends on it. With its help, the optimum 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 become the cause, albeit indirect, of the failure of the power unit.
Checking a two-pin engine temperature sensor VAZ-2115 is more painstaking and time-consuming. It is produced in the following sequence:
- First you need to find the sensor, which is located on the pipe between the cylinder head and thermostat.
- For greater convenience and safety, it is necessary to remove the air filter and remove the terminals from the battery.
- Drain coolant into a suitable container.
- Disconnect the connector from the sensor.
- Unscrew the sensor from the seat with a 19 spanner.
- Take a liquid thermometer, a multimeter and any device designed to heat water.
- We fasten wires of a suitable diameter and length to the sensor contacts. We fix their other ends on the probes of the multimeter.
- Using the switch, we set the limit of 20 kOhm on the device.
- We lower the sensor into the water, the contacts must remain dry. We warm the liquid and monitor the readings of the thermometer and multimeter. They should correspond to those given in the table.
Temperature (deg.) | twenty | 40 | 60 | 80 | one hundred |
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, reaching the next control point, it is better to stop heating for a few seconds and wait for the multimeter to read stable values. In addition, the temperature values are shown 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 the case of obvious signs indicating its malfunction. In the event of any engine malfunction, the more probable causes should first be ruled out and only the “suspect” of the DTOZh should be the last.