Sensor for coolant temperature indicator: location, check, replacement

The modern automobile engine operates on the commands of a single electronic control unit. This command center adjusts individual parameters based on information coming from different sensors. One of these elements that directly affect the performance of the engine is the sensor of the coolant temperature gauge. It captures and transmits signs of overheating so that the ECU corrects the operation of the ICE.

What is the coolant temperature sensor

The element is made by a single unit with a body on the thread, which is screwed into the motor (sometimes - into the thermostat or radiator) and directly contacts the engine cooling fluid. During operation, the engine heats up, and the antifreeze, respectively, cools it. Circulating through special channels inside the cylinder block, the liquid heats up, while giving this heat in the radiator. The sensor registers the amount of heating of the coolant. This information is sent to the computer in the form of indirect heating of the engine. Information about what temperature it is used to correct the ICE control program. It should be understood that this sensor does not measure the temperature of the directly metal of the engine (it is much larger), but the degree of heating of the fluid flowing through it.

How does the feedback system work?

The engine management system is a flexible self-learning program that forms the parameters of the ICE dynamically, that is, based on real-time sensor readings. With respect to the motor, the system draws conclusions about whether the unit is warmed up or, conversely, its temperature is still insufficient to use the maximum power mode.

What affects the operation of the sensor

• The temperature of the coolant is one of the factors that affect the correction of the engine. Thanks to signals from this element, the following indicators change:
• Enrichment of the fuel mixture. If a low coolant temperature signal is output from the sensor, the program recalculates the fuel quantity for the injectors upwards. The cold engine works more stable at increased idle.
• An advance of ignition. The ECU calculates the advance angle based on the current load and the degree of warm-up of the motor. On a cold engine, the UOZ will be less. Incorrect operation of the sensor will also affect this parameter. This, in turn, will lead to unstable operation of the motor in all modes, to a decrease in power and an increase in fuel consumption.
• Cooling fan operation. High temperatures of the liquid (antifreeze) give the command to turn on the fan that blows the radiator. If the indication is incorrect, the element will not work correctly. In case of overheating, the fan may not turn on, as, according to the sensor, the heating is small. And this is fraught with serious consequences until the deformation of the cylinder head.

Where is the item

Find out where the coolant temperature sensor is located is quite simple. The element is installed in two places - on the cylinder block of the engine or on the thermostat housing. In both cases, reliable information about the heating of the engine is provided. For example, the coolant temperature sensor "Renault Logan" or "Renault Sandero" is located near the first cylinder at the end of the cylinder block. This element is doubled. It gives a signal for the indicator on the instrument panel and for the computer system. If it is the coolant temperature sensor "Opel", then in these cars the element is installed in the tank of the main radiator. There are two such sensors on the V-shaped engine. They put one for each row of cylinders. Sometimes a second, similar sensor is used to turn on the radiator fan. It performs one function - it controls the time when the fan is switched on.

Varieties

The sensor of the coolant temperature indicator is a thermistor. It changes its resistance, depending on the heating of the liquid with which it comes into contact. In this case, materials are used that reduce their resistance when heating is increased. In other devices, elements based on other principles are used, 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 the car. On average, it is 400-500 rubles.

Diagnosis of operability

Sometimes it happens that the reading element begins to clearly overstate or underestimate the readings. Before checking the coolant temperature sensor, you should make sure that it is he who is responsible for the problems. To do this, you must consistently exclude all other reasons. First of all, this is a problem with electrical wiring. Also, many problems with engine warming cause the thermostat to work and the appearance of air congestion 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 a situation, for the ECU the readings are often taken directly from the measuring device.

Methods for testing the operability

So, how do I check the coolant temperature sensor? Since it is a thermistor, it is diagnosed by an ohmmeter (multimeter in the ohmmeter mode). For each particular sensor (or its type), there is a resistance-temperature relationship. By connecting a multimeter to it, determine the resistance at 20 degrees, and then lower the element into a glass with boiling water. The resistance should be greatly reduced, according to the table in which the tolerances of the values are indicated. If they go beyond, the sensor needs to be replaced. Also, the element should be checked for a short circuit. If it is available, the part is unequivocally unfit for work.

Replace the element with your own hands

The sensor of the coolant temperature gauge changes quite easily. Despite the fact that on each engine its location is different, the general principle is the same. It is better to replace the element with your own hands on a cold engine. Unplugging the terminal block with wires and a wrench is used to unscrew the sensor. The new element must be kept ready, so as not to miss a lot of antifreeze from the hole.

It should be noted that a sealing metal or brass ring is mounted on the threaded part, which should also be replaced. It comes complete with a sensor. Taking out the old sensor, in its place, screw in a new one, with a pre-applied ring and a threaded part with a greased sealant. That is why the motor must be cold when carrying out work. Heated tosol burns more than boiling water. After this, you can put the shoe in place and top up the missed tosol.

The result

As you can see, the sensor of the coolant temperature indicator is a simple but very important component of the control system. It depends on the smooth and reliable operation of the engine.