Strictly speaking, water temperature sensors are divided into two categories. No matter what its internal structure is a thermistor, its resistance is between 275 ohms and 6500 ohms. Moreover, the lower the temperature, the higher the resistance, and the higher the temperature, the lower the resistance.
The first type of water temperature sensor is relatively simple in that it changes the change of the current through the change of the resistance of the sensor to drive the change of the water temperature meter, and indirectly tells the working temperature of the engine. In the second category, the water temperature sensor has no structural change, but its function is to provide an analog signal of temperature change to the engine control unit. Its supply voltage is the 5V power supply provided by the control unit, and the signal returned to the control unit is a linear change signal of 1.3V-3.8V. The main role is to tell the engine control unit what the temperature is now. Conversely, its signal is important to the control unit. Mainly the engine has different working methods at different working temperatures. For example, if the engine is below 86 degrees, the engine should be sprayed 10% more than the normal temperature. The purpose is to let the engine heat up quickly to reduce the low temperature wear of the engine. And when the temperature rises above 86 degrees, it is necessary to let the engine spray less oil, so that the temperature regeneration is slower. So its role is very important. If he has a problem, he will send a wrong signal to the engine control unit. For example, if the engine provides a low temperature signal when the vehicle is hot, whether your car is more oily, it seems a bit waste oil.
But these two water temperature sensors work under different voltage conditions. The sensor for the water supply thermometer is 12V, and the engine control unit uses 5V, so they are not interchangeable. Moreover, their plug shape itself is different.
To distinguish them is very simple. The former has only one wire in the plug, while the latter has two wires in the plug for the engine control unit.
The water temperature and water level sensor is composed of a thermostat part and a water level control part, and is also equipped with a decompression device in front of the electric valve and a rotary muffler heater for heating.
The water level sensor in the container transmits the sensed water level signal to the controller, and the computer in the controller compares the measured water level signal with the set signal to obtain a deviation, and then issues a warning to the water supply electric valve according to the nature of the deviation. The ""off" command is turned on to ensure that the container reaches the set water level. After the water inflow procedure is completed, the temperature-controlled portion of the computer issues an "open" command to the electric valve that supplies the heat medium, and the system begins to heat the water in the container. When the temperature is set. The controller issues a command to close the valve, cut off the heat source, and the system enters the holding state. During the programming process, ensure that the system does not open the electric control valve that controls the heat source without reaching the safe water level, thus avoiding heat loss and accidents.
The function of the water temperature sensor is to convert the temperature of the cooling water into an electrical signal. After inputting into the ECU, there are:
1. Correct the fuel injection amount; increase the fuel injection amount when the temperature is low.
2. Correct the ignition advance angle; increase the ignition advance angle at low temperature, and delay the explosion to prevent deflagration.
3. Influence the idle speed control valve; when the temperature is low, the ECU controls the idle speed control valve according to the water temperature sensing signal to improve the speed change.
4. Affect the EGR valve.
Identification and detection
The thermistor type water temperature meter consists of a thermistor type water temperature sensor and a bimetal, as shown in Figure 1. Among them, the thermistor is the sender of the water temperature information, and the bimetal electric heating wire is the receiving member, and the two are connected in series. The sending water temperature sensor is installed in the waterway and is in contact with the cooling water. When the water temperature is low, the thermistor value is high, the current in the circuit is small, the heat generation of the resistance wire is small, the bimetal is slightly bent, and the indicator pin is at a low temperature. District (C District). When the water temperature is high, the thermistor value is small, the current passing through the circuit is large, the heat generation of the resistance wire is large, the bimetal sheet has a large bending deformation, and the indicator needle points to the high temperature region (H region).
The water temperature sensor used in the water temperature meter is a negative temperature coefficient thermistor, which is installed in the water jacket of the cylinder head and the water temperature sensor of the water temperature meter.
1 Thermistor type water temperature meter
1 thermistor; 2. information transmitter; 3 bimetal; 4. indicator pin; 5 information receiver
1 thermistor; 2 a conductive sleeve; 3 conductive spring; afternoon copper joint; s-g tube; 6 end button; 7. conductive rod;
Water temperature meter water temperature sensor, the terminal is connected with the water temperature meter, and the other end is grounded through the sensor casing.
When the engine water temperature is low, the water temperature sensor of the water temperature meter inputs the ECU's water temperature information to make the air-fuel ratio richer, so that the engine works stably. If the water temperature sensor does not generate cold state information at this time, the air-fuel ratio will be thinned, resulting in the engine. Not working properly. Similarly, if the chiller information is sent after warming up, the air-fuel ratio will be enriched and the engine will not work properly.
When the water temperature sensor fails, the temperature signal of the hot car is often displayed when the cold car starts. The ECU can't get the signal of the rich mixture, and can only supply the lean mixture of the engine (the signal when the car is hot). Therefore, the engine cold car is not easy to start. In this case, check if the water temperature sensor plug is in contact or replace the water temperature sensor.
For example, reading the static engine of the car (referring to the cold car) data found that the engine ECU output coolant temperature is 105 ° C, and at this time (set is the winter temperature) the actual temperature of the engine is only 1 ° C, Obviously, the water temperature signal received by the engine ECU is wrong, indicating a problem with the water temperature sensor.
It should be noted that the sensor is an electronic original device on the automobile circuit. If the device is broken, there is not much room for repair, and only the replacement is made. If you want to test it, the simple method is to put the water temperature sensor in the heating cup to heat it (be careful not to submerge the plug part), use the multimeter's "resistance gear position" to measure, when the temperature rises, the resistance should be smaller. If there is no change, it proves that this thing is broken.
If this component is detected with a diagnostic tool, it needs to be detected while cold.
The function of the water temperature sensor is to convert the temperature of the cooling water into an electrical signal. After inputting to the ECU, there is: 1. Correct the fuel injection amount; increase the fuel injection amount when the temperature is low. 2. Correct the ignition advance angle; increase the ignition advance angle at low temperature, and prevent it from deflagrating at high temperatures. 3. Influence the idle speed control valve; when the temperature is low, the ECU controls the idle speed control valve according to the water temperature sensing signal to increase the speed.