A modern car engine operates on the instructions of a single electronic control unit. This command center corrects individual parameters based on the information received from various sensors. One of these elements that directly affect engine performance is the coolant temperature gauge sensor. It captures and transmits signs of overheating so that the computer corrects the operation of the internal combustion engine.
What is a coolant temperature sensor
The element is made as a single unit with a threaded housing, which is screwed into the engine (sometimes into a thermostat or radiator) and is in direct contact with the engine coolant. During operation, the engine heats up, and antifreeze, respectively, cools it.
By circulating through special channels inside the cylinder block, the fluid heats up, and at the same time gives off this heat to the radiator. The sensor records the amount of heating of the coolant. This information is received in the computer in the form of indirect engine heating. Information about what temperature it is used to correct the internal combustion engine control program. It should be understood that this sensor does not measure the temperature of the engine metal directly (it is much larger), but the degree of heating of the fluid flowing through it.
How the feedback system works
The engine management system is a flexible self-learning program that generates the parameters of the internal combustion engine dynamically, i.e. based on real-time sensor readings. With regard to the motor, the system draws conclusions about whether the unit is warm or, conversely, its temperature is still insufficient to use the maximum power mode.
What affects the operation of the sensor
- Coolant temperature is one of the factors affecting the correction of engine operation. Thanks to the signals from this element, the following indicators change:
- The enrichment of the fuel mixture. If the sensor receives a signal about a low coolant temperature, the program recalculates the amount of fuel for the injectors in the direction of increase. A cold engine runs more stably at high idle.
- Ignition timing The computer calculates the lead angle based on the current load and the degree of warming up of the motor. On a cold engine, the UOZ will be less. Incorrect sensor operation will also affect this parameter. This, in turn, will lead to unstable operation of the motor in all modes, to reduce power and increase fuel consumption.
- The operation of the cooling fan. High temperatures of the liquid (antifreeze) give the command to turn on the fan blowing the radiator. If the readings are incorrect, the operation of the element will be incorrect. During overheating, the fan may not turn on, since, according to the sensor, the heating is small. And this is fraught with serious consequences up to the deformation of the cylinder head.
Where is the item
Finding out where the coolant temperature sensor is located is pretty simple.
The element is installed in two places - on the engine block or on the thermostat housing. In both cases, quite reliable information on engine heating is provided. For example, a Renault Logan or Renault Sandero coolant temperature sensor is located near the first cylinder at the end of the cylinder block. This item is dual. It gives a signal for the indicator on the instrument panel and for the computer system. If this is an Opel coolant temperature sensor, then in these cars the element is installed in the tank of the main radiator.
There are two such sensors on the V-shaped ICE. Put one on each row of cylinders. Sometimes a second, similar sensor is used to turn on the radiator fan. It performs one function - it regulates the moment the fan is turned on.
Varieties
The gauge for the coolant temperature gauge is a thermistor. It changes its resistance depending on the heating of the liquid with which it is in contact. In this case, materials are used that reduce their resistance with increasing heating.
Other devices use elements based on different principles, but in automotive engines such thermistors are the simplest and most reliable. The price of the coolant temperature sensor varies depending on the brand of car. On average, it is 400-500 rubles.
Health Diagnostics
Sometimes it happens that the reading element begins to clearly overestimate or underestimate the readings. Before checking the coolant temperature sensor, make sure that it is he who is the culprit.
To do this, we must consistently exclude all other causes. First of all, these are problems with the wiring. Also, many problems with engine warming are caused by the operation of the thermostat and the appearance of air jams in the SOD. It should be borne in mind that the indicators of the arrow or indicator on
the instrument panel serve only to orient the driver in the situation; for the computer, readings are often taken directly from the measuring device.
Health Check Methods
So, how to check the coolant temperature sensor ? Since it is a thermistor, it is diagnosed with an ohmmeter (multimeter in ohmmeter mode). For each specific sensor (or its type) there is a dependence of resistance on temperature.
By connecting a multimeter to it, determine the resistance at 20 degrees, and then lower the element into a glass of boiling water. The resistance should decrease significantly, according to the table in which the tolerances of the values are indicated. If they go beyond, then the sensor needs to be replaced. Also, the element should be checked for a short circuit. If available, the part is clearly unsuitable for work.
DIY item replacement
The coolant temperature gauge sensor changes quite simply. Despite the fact that its location is different on each engine, the general principle is the same.
Do-it-yourself replacement of the element is best done on a cold engine. Having disconnected a block with wires, the sensor is unscrewed with a wrench. The new element must be kept ready so as not to miss a lot of antifreeze from the hole.
It should be noted that on the threaded part a sealing metal or brass ring is installed, which is also desirable to replace. It comes with a sensor. Having taken out the old sensor, a new one is screwed in its place, with a pre-worn ring and a threaded part greased with sealant. That is why the motor must be cold during work. Heated antifreeze burns harder than boiling water. After that, you can put the block in place and add the lost antifreeze.
Total
As you can see, the coolant temperature gauge sensor is a simple, but very critical component of the control system. Uninterrupted and reliable operation of the engine depends on it.