The important role of car coolant temperature sensor not everyone knows

The important role of car coolant temperature sensor not everyone knows


Car coolant temperature sensor is very important not only in the cooling system.

Function and structure of sensor for cooling water temperature

Auto coolant temperature sensor is one of the types of automotive sensors that play an important role. The location of the coolant temperature sensor is usually located in the tap of the tap and has the function of measuring the coolant temperature, then transmits that information to the microprocessor so that it can calculate and adjust the ignition angle and running speed. No load … For some modern vehicles, cooling water temperature parameters are also used to control the exhaust control system. Some specific parameters that the machine coolant temperature controls are:

Early ignition angle: When the cooling water temperature is low, the central processing unit (ECU) will make adjustments to increase the early ignition angle to raise the water temperature. Otherwise, ECU will adjust the ignition angle again to regulate.

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Fuel injection time: If the cooling water temperature parameter is low, ECU will adjust to increase fuel injection time. If re-watering, ECU will reduce the time to refuel.

Position the bonus coolant temperature sensor next to the water compartmentPosition the bonus coolant temperature sensor next to the water compartment

No-load speed: When the engine starts to move, the cooling water temperature will be low, so the ECU will control to increase the idle valve, to heat the engine and reduce friction in other parts while helping the car. achieve optimal operating temperature quickly.

Regarding the cooling water temperature sensor structure, this part will be hollow cylinder with external thread. Inside the sensor is a thermistor with a negative resistance coefficient.

Principle of cooling water temperature sensor

This sensor will have a way to measure car coolant temperature based on the resistance factor. That is, when the water cooling temperature is low, the sensor resistance will be high and vice versa. Then the voltage applied at the bottom of this sensor will change based on that resistor.

Sensor and working principleSensor and working principle

5V voltage will flow through the standard resistor (does not change based on temperature) then will run through the thermistor (in the sensor) and cooling water temperature sensor circuits send information about the ADC converter (analog signal converter). Thus, the ADC will receive information about temperature parameters based on the voltage bridge generated from the standard resistor and thermal resistance in the sensor and from there will forward to the central processing system (ECU), to indicate whether the vehicle is having a high or low cooling water temperature.

See 89% more of the car cooling system, which often suffers from these problems

How to check the coolant temperature sensor

To be able to check whether the cooling water temperature sensor is working properly, we must use a resistive meter. Resistor meter helps to record the change of resistance when changing the temperature based on parameters that the manufacturer has provided before. Vehicle owners can use simple heat sources to test such as hot water mugs, light fire and check if the resistance varies according to the heat source.

Check cooling water temperature sensorCheck cooling water temperature sensor

According to car maintenance experience, if the heat source is high, the sensor changes resistance from 0.2 to 0.3, the sensor works normally. If the cold source is added and the resistance increases to 4.8 – 6.6, the sensor will operate normally.

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Common causes of errors in coolant temperature sensors

When the cooling water temperature sensor has malfunctioned, it usually comes from causes such as broken sensor, broken wire or positive touch. At that time, if you want to check, the car owner needs to open the sensor to see if there is water leakage. If this problem is ignored, ECU can understand that the cooling water temperature is low and open the time of high fuel injection causing gas clogging.

Minh Tan

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