A modern refrigerator is complex an electronic organism whose work is dependent on the accurate readings of many sensors. If previously temperature control was carried out by a primitive mechanical thermostat, today electronic module receives data from a whole network of measuring instruments. Understanding which sensors are installed in your model is the key to self-diagnosis of most cooling or defrosting problems.
Failure of even one element can lead to food spoilage, freezing of the evaporator, or constant wear and tear of the compressor. In this article we will analyze in detail the design of the sensor system, consider working principle various types of temperature and humidity meters, and also learn how to identify malfunctions without calling a technician. Knowing where they are and what they look like thermoresistorswill help you save a significant amount on repairs.
Main types of temperature sensors
The control system is based on a temperature sensor, which most often a thermistor (NTC). Its resistance changes depending on the ambient temperature, allowing the electronic control unit (ECU) to read accurate data in degrees Celsius. Unlike old mechanical thermostats, thermistors do not have moving contacts, which makes them more reliable, although susceptible to power surges in the network.
The number of sensors directly depends on the functionality of the refrigerator. Simple models may have one or two sensors, while complex systems No Frost with a freshness zone and an ice maker are equipped with a whole network of 5-8 measuring elements. Each of them is responsible for its own section: the evaporator of the freezer, the main refrigerator, the air cooling zone, or even the temperature of the incoming flow.
It is important to understand that calibration these devices are manufactured factory, and their readings have an acceptable error. If the refrigerator begins to “lie” with the temperature, most often it is a failure in the thermistor readings that is to blame, and not a breakdown of the compressor. The electronics simply receive the wrong signal and make an erroneous decision to turn the motor on or off.
Sensors of the automatic defrost system (Defrost)
One of the most critical groups of sensors are the elements that control the defrosting cycles of the evaporator. In systems No Frost ice is inevitable on the evaporator, and a heater is used to remove it. To prevent this heater from burning the plastic or overheating the system, the process is monitored by defrost sensor (defroster).
Usually it is attached directly to the evaporator tubes or inserted into a special hole in it. Its task is to signal to the control module that the ice has melted and the temperature has reached a certain threshold (usually +5...+10°C). After this, the ECU turns off the heating element and starts the fan for drying or immediately switches to cooling mode.
⚠️ Attention: If the defrost sensor is “stuck” in the “open” position, the refrigerator will not be able to exit the defrost mode, and the food in the freezer will begin to melt. If it is constantly closed, the defrost will not turn on, and the evaporator will become overgrown with a “fur coat.”
The second important element of this system is evaporator temperature sensor. It controls the cooling process while the compressor is running. When the temperature at the evaporator drops to a predetermined minimum (for example -18°C), this sensor commands the compressor to stop. The joint operation of these two elements ensures stable temperature conditions and the absence of ice in the air ducts.
Sensors in two-chamber and multi-chamber models
In refrigerators with two or more chambers, the number of sensors increases in proportion to the number of independent cooling zones. This is where the principle of separate control comes into play. One thermal sensoris responsible for the temperature in the freezer compartment, and the other for the refrigerator compartment. This allows the system to compensate for temperature changes when opening the doors.
In models with technology Twin Cooling or similar, where two air circulation circuits are used, additional sensors can be installed in the air supply channels. They adjust the dampers, directing the cold flow to where it is needed at the moment. This ensures a more uniform distribution of cold and the absence of drafts that dry out food.
Particular attention should be paid to sensors in the “zero temperature” or “freshness” zone. In this compartment, the requirements for measurement accuracy are maximum, since even a small deviation can lead to spoilage of meat or fish. Precision sensors in this area they work in conjunction with a separate fan or damper, maintaining the temperature strictly within 0...+2°C.
Why do sensors go out of order? building?
The main reason is oxidation of contacts due to moisture or microcracks in the thermistor housing from constant cycles of expansion and contraction during temperature changes.
Sensors for inverter compressors
Modern inverter refrigerators are equipped with an even more complex diagnostic system. The compressor itself in such models often has built-in sensors that transmit data on the temperature of the windings and the rotor speed. This is necessary for a smooth start and to protect the engine from overheating.
If inverter module receives a signal about critical overheating or a malfunction of the Hall sensor (which controls the rotation speed), it can block the start of the compressor. In this case, the refrigerator will emit a sound signal or flash indicators on the control panel, indicating an error.
Diagnostics of such systems requires special equipment, since conventional multimeters cannot always correctly read the pulse signal from the inverter sensors. However, visual inspection of the wiring and checking the resistance of static temperature sensors can often identify the problem without deep intervention in the electronics.
| Sensor type | Location | Function | Resistance (example) |
|---|---|---|---|
| Refrigeration chamber thermostat | Inside the chamber, at the back wall | Air temperature control | 5-10 kOhm at +25°C |
| Defroster (defrost) | On the freezer evaporator | Turning off the heating element when the ice melts | Closes at +5°C |
| Evaporator sensor | Built into the evaporator | Freon cooling control | Varies linearly |
| Environment sensor | Inside the case, near the ECU | Correction of operation in hot/cold | Depends on the model |
Diagnostics and serviceability check
Checking sensors begins with an external inspection. It is necessary to ensure that the wires are intact and that there are no traces of melting or oxidation on the contacts. Often the problem lies not in the sensor itself, but in an open circuit or poor contact in the connector that connects wire harness to the control board.
For an accurate check, use a multimeter switched to resistance measurement mode (Ohm). The sensor is removed from the mounting location and its resistance is measured at room temperature. Then you can place it in a glass with warm water and observe how the resistance changes - it should gradually decrease when heated.
☑️ Sensor diagnostics
If the resistance is infinite (open) or zero (short circuit), the part must be replaced. It is also worth paying attention to the tightness of the sensor housing. If moisture gets inside, the readings will be incorrect, and it is better to replace it preventively, even if it shows resistance. thermistor It is better to replace it preventively, even if it shows resistance.
Replacement and nuances of installing new parts
When replacing a sensor, it is extremely important to choose an analogue with similar characteristics. Although many thermistors look similar, their resistance curves may differ. Installing an unsuitable sensor will result in the refrigerator operating in the wrong mode, for example, turning off at -5°C or not turning off at all.
The junction of the new sensor with the evaporator tube or chamber wall must be carefully sealed. For this, a special thermally conductive adhesive or sealant is used. Thermal contact must be maximum so that the sensor quickly responds to changes in the temperature of the metal, and not the air around it.
⚠️ Attention: Never use ordinary silicone sealant to fix sensors without thermal conductive properties or metal clamps, which can damage the thin sensor housing.
After installing and connecting all connectors, the refrigerator should be turned on and monitored for several hours. It is advisable to use an external thermometer to check the actual temperature in the chambers to ensure that the new part is working correctly.
Frequently asked questions (FAQ)
Is it possible to operate a refrigerator with a faulty sensor?
Short-term - yes, but it is risky. A faulty defrost sensor will cause the evaporator to freeze and cause fan or compressor failure within a few days. The temperature sensor can cause food to defrost or freeze.
Why does the refrigerator not work correctly after replacing the sensor?
A sensor with a different resistance rating may be installed. The tightness of the fit could also be broken, causing the sensor to measure the temperature of the air rather than the evaporator wall. Check the quality of the installation.
How often do you need to change the sensors in the refrigerator?
They do not have a strict service life. They are replaced only when they break down. With normal operation and a stable network voltage, they can last 10-15 years or more without replacement.
Does humidity in the chamber affect the operation of the sensors?
The sensors themselves are sealed, but oxidation of the contacts in the connectors due to high humidity is a common cause of failures. It is recommended to periodically check the condition of the contact groups.