Strictly speaking, water temperature sensors are divided into two categories.Whatever its internal structure isThermistorIts resistance is between 275 ohms and 6500 ohms.The lower the temperature, the higher the resistance, and the higher the temperature, the lower the resistance.
The function of the first type of water temperature sensor is relatively simple, which is to change the resistance of the sensor to change the current to drive the change of the water temperature meter, indirectly telling people about the engineworking temperature 。Second, the water temperature sensor has no structural change, but its function is tocontrol unit Provide a temperature changingAnalog signal。itsSupply voltageIt is a 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 function is to tell the temperature of the engine control unit.Conversely, its signal is extremely important to the control unit.The main reason is that the engine has differentWorking methods。For example, the engine temperature below 86 ℃ is higher than the normal temperatureMultiple sprayingThe purpose of 10% oil is to quickly heat up the engine to reduce the low temperature wear of the engine.When the temperature rises above 86 degrees, the engine should be sprayed with less oil, and the temperature regeneration should be slow.So its role is very important.If he has a problem, he provides wrong signals to the engine control unit. For example, he provides the engine low temperature signal when the car is hot. Does your car need to inject more fuelWaste oilla
However, these two water temperature sensors work under different voltage conditions. The sensor used for the water supply thermometer is 12V, while the sensor used for the engine control unit is 5V, so they cannot be interchanged.Moreover, their plugs are different in shape.
To distinguish them, it is very simple that there is only one wire in the plug of the former and two wires in the plug of the latter for the engine control unit.Don't make mistakes.
The water level sensor in the vessel 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 the deviation. Then, according to the nature of the deviation, it sends the "open" and "close" instructions to the electric water supply valve to ensure that the vessel reaches the set water level.After the water inflow procedure is completed, the computer of the temperature control part suppliesHeat mediumThe electric valve of the valve sends out the "open" command, so the system starts to heat the water in the container.reachsetting temperatureWhen.Only when the controller sends the order of closing the valve and cutting off the heat source, the system enters the thermal insulation state.During programming, ensure that the system can control the heat source without reaching the safe water levelElectric control valveThe valve is not opened, thus avoiding heat loss and accidents.
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The function of the water temperature sensor is to convert the cooling water temperature into an electrical signal. After input into the ECU, there are:
1. Correct the fuel injection quantity;Increase the injection quantity when the temperature is low.
2. CorrectionIgnition advance angle；The ignition advance angle shall be increased at low temperature, and delayed at high temperature to prevent deflagration.
3. ImpactIdle speed control valve；At low temperature, the ECU controls the action of the idle speed control valve according to the water temperature sensing signal to improve the speed.
ThermistorType A water temperature gauge consists of a thermistor type water temperature sensor and aBimetallic sheetComposition, as shown in Figure 1.Among them, thermistor is the transmitter of water temperature information, bimetallic sheetElectric heating wireIt is a receiving piece, and they are connected in series.The transmitter, namely the water temperature sensor, is installed in the water channel to contact the cooling water. When the water temperature is low, the thermistor value is high, and the current in the circuit is low,Resistance wireOfCalorific valueSmall, the bimetallic sheet is slightly bent, and the indicator pin is in the low temperature zone (Zone C).When the water temperature is high, the thermistor value is small, the current passing through the circuit is large, the heating capacity of the resistance wire is large, and the bimetallic sheetBending deformationLarge, indicating needle points to high temperature area (H area).
The water temperature sensor is used for the water temperature gauge. Its terminal is connected to the water temperature gauge, and the other end is grounded through the sensor housing.
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When the engine water temperature is low, the water temperature sensor of the water temperature gauge sends the water temperature information to the ECUAir-fuel ratioIt will become thicker, so that the engine can work stably. If the water temperature sensor does not freeze at this timestatus information , the air-fuel ratio will become lean, resulting in abnormal engine operation.Similarly, ifWarm upAfter sending a cold engine message, the air-fuel ratio will become richer and the engine will not work properly.
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When the water temperature sensor fails, it usually displays the temperature signal when the cold car starts, but the ECU cannot provide itConcentrated mixtureThe signal of can only be supplied to the thinner engineMixture(signal when the car is hot), so it is difficult to start the engine when the car is cold.In this case, check whether the water temperature sensor plug contacts normally or replace the water temperature sensor.
For example, when reading the static engine data of the vehicle (referring to cold car), it is found that the engine ECU outputsCoolantThe temperature is 105 ℃, but the actual temperature of the engine is only 1 ℃ at this time (set as the temperature in winter). It is obvious that the water temperature signal received by the engine ECU is wrong, indicating that there is a problem with the water temperature sensor.
It should be noted that the sensor is a kind of original electronic device on the automobile circuit. If the device is broken, there is little room for repair, so it has to be replaced.If you want to test it, the simple method is to put the water temperature sensor into the heating cup for heating (be careful not to submerge the plug part), and useA multimeterWhen the temperature rises, the resistance should be smaller. If there is no change, it means that the thing is broken.
If usedScan toolTo detect this component, it needs to be detected when the vehicle is cold.
The function of the water temperature sensor is tocooling waterTemperature conversion toelectrical signal, EnterECUAfter that: 1.Correct the fuel injection quantity;Increase the injection quantity when the temperature is low.2。Correct ignition advance angle;The ignition advance angle shall be increased at low temperature, and delayed at high temperature to prevent deflagration.3. Affect idle speed control valve;At low temperature, the ECU controls the action of the idle speed control valve according to the water temperature sensing signal to increase the speed.
