The coolant temperature sensor is designed to measure the coolant temperature in the engine cooling system. The sensor is included in the engine management system.
The information from the sensor is used by the control system to correct the main parameters of the engine operation depending on the thermal state:
- Crankshaft speed;
- The qualitative composition of the fuel-air mixture;
- Ignition timing.
Thus, the operation of the coolant temperature sensor ensures that the engine warms up quickly at start-up and maintains its optimum temperature in all modes.
Currently, the coolant temperature sensor is an element of the electronic control of the cooling system, with the help of which the engine temperature is continuously monitored and regulated. A thermistor is used as a sensor – a resistor that changes resistance depending on temperature.
The thermistor is made of semiconductor materials (nickel oxide, cobalt oxide), which are characterized by an increase in free electrons with increasing temperature and, accordingly, decreasing resistance. The thermistor is placed in a protective heat-conducting case, on which a fastening thread and an electrical connector for connection are made.
The thermistor has a negative temperature coefficient, i.e. its resistance decreases with increasing temperature. When the engine is cold the resistance of the sensor is maximum. A voltage of about 5V is applied to the sensor, which decreases with a change in the resistance of the sensor. The engine control unit calculates the coolant temperature from the voltage drop across the sensor.
The coolant temperature sensor is screwed into the cylinder head outlet. New temperature control possibilities are opened up with the use of two coolant temperature sensors. One of the blackhawk supply sensors is installed at the engine outlet, the other at the radiator outlet.
The required coolant temperature is determined depending on the engine load (air intake mass) and the engine speed. According to the readings of the sensors, the nature of the fan operation, the degree of opening of the thermostat, the switching on of the relay of the additional cooling pump in the exhaust gas recirculation system, and the engine cooling relay after stopping are determined.