Temperature sensor in a refrigerator: device, principle of operation and fault diagnosis

A refrigerator is not just a box with a freezer, but a complex system where each element plays a key role in maintaining optimal conditions for storing food. The central place in this system is occupied temperature sensor, which is responsible for ensuring that the compressor turns on and off at the right time. Without it, the refrigerator will either turn into a freezer or become a warm cupboard, and food will quickly spoil.

But how exactly does this little device determine when to cool the chamber and when to let it rest? Why does the refrigerator sometimes start to wear out, not turning off for hours, or, conversely, stop freezing? The answers lie in the principle of operation of the sensor, its types and possible malfunctions. In this article we will look at:

• 🔍 How it works how the temperature sensor works in modern refrigerators;
• 📊 What types of sensors used in different models (from mechanical to electronic);
• ⚠️ Signs of breakdown and how to distinguish them from others malfunctions;
• 🛠️ Is it possible to check and replace the sensor on your own, without calling a technician.

If your refrigerator begins to behave strangely - it freezes too much, cools poorly or makes unusual sounds - the problem may lie in the sensor. Next, you will learn how to diagnose it and what to do next.

What is a temperature sensor and why is it needed?

A temperature sensor (or thermostat, thermostat, temperature sensor) is a device that measures the temperature inside the refrigerator or freezer compartment transmits data to the control board. Based on this data, the compressor is turned on or off, maintaining the set mode.

Simpler speaking, the sensor performs three key functions:

• 🌡️ Controls the current temperature in the chamber;
• 📶 Compares it with the set value (for example, +4°C for the refrigerator compartment);
• 🔌 Gives a command to the compressor at startup or stop.

Without the sensor, the refrigerator would not be able to automatically maintain the desired climate. For example, if you open the door and warm air gets inside, the sensor will “notice” this and turn on the cooling. When the temperature returns to normal, the compressor will turn off. This cycle is repeated dozens of times a day.

⚠️ Attention: In older models of refrigerators (before the 2000s), gas-filled ones were often used instead of electronic sensors. Their operating principle is different, and they more often fail due to wear. mechanical thermostats with gas filling. Their operating principle is different, and they are more likely to fail due to wear and tear.

Types of temperature sensors in refrigerators

Modern refrigerators are equipped with different types of sensors, which differ in principle of operation and accuracy and reliability. Here are the main types:

Most household refrigerators today use electronic thermistorsThey are a small resistor, the resistance of which changes when heated or cooled. For example, models Samsung RB30J3000WW or LG GA-B489YGQZ usually have a sensor NTC thermistor (with a negative temperature coefficient).

Mechanical thermostats can still be found in budget or outdated models. Their main advantage is simplicity: if such a sensor breaks, it is easy to replace even without special skills. However, the accuracy leaves much to be desired, so modern manufacturers refuse them.

Where is the temperature sensor in the refrigerator

The location of the sensor depends on refrigerator model and the type of cooling system. In most cases, it can be found in the following places:

• 🔹 Refrigerator compartment: inside the plastic case on the back wall, next to the lamp. lighting or on the top panel;
• ❄️ Freezer compartment: often hidden behind a protective cover on the evaporator (in models with No Frost);
• 🔌 External unit: in refrigerators with electronic control, the sensor can be placed on the control board (for example, in Liebert or Haier).

In refrigerators with a system No Frost usually installed several sensors:

• One controls the temperature in the refrigeration room chamber;
• The second is in the freezer;
• The third monitors the operation of the evaporator (defrost sensor).

To accurately find the sensor in your model, you can:

1. Look in operating instructions (section "Parts layout");
2. Remove the rear panel of the refrigerator compartment (in most models the sensor is mounted on clips or screws);
3. Refer to service manual (for example, for Samsung or LG they can be found in the public domain according to the model).

⚠️ Attention: In refrigerators with a system Full No Frost (for example, Bosch KAN92VI30R) sensors are often hidden behind panels with air ducts. Do not try to get them without turning off the power - there is a risk of damaging the wiring!

What does a temperature sensor look like?

Usually it is a small plastic cylinder (the size of a little finger) with two wires, less often - a flat plate B. in mechanical thermostats, this can be a metal tube with a capillary leading to the regulator.

How the sensor works: a step-by-step process

Let's look at how the sensor interacts with other parts of the refrigerator using an example electronic system (the most common option in modern models).

1. Temperature measurement. The sensor (for example, NTC thermistor) constantly reads the temperature of the air in the chamber. Its resistance changes: as the temperature decreases, it increases, as it increases, it decreases.
2. Signal transmission. Data is received at control board (the brain of the refrigerator), where they are compared with a set value (for example, +4°C for the refrigerator compartment).
3. Analysis and command. If the temperature is higher than normal, the board sends a signal to start relay, which starts the compressor. If the temperature is normal, the compressor turns off.
4. The cycle is repeated. The process occurs continuously, at intervals of several seconds.

In mechanical systems the principle is similar, but instead of electronics a gas thermostat is used gas thermostat:

• Inside the thermostat there is freon or another gas that expands when heated;
• When the critical temperature is reached, the gas presses on the membrane, which opens the contacts;
• The compressor turns off until the temperature rises again.

In refrigerators with the No Frost system, a defrost sensor additionally monitors the formation of ice on the evaporator. If the evaporator temperature drops below -10°C, the defrost heater turns on.

Signs of a malfunctioning temperature sensor

If the temperature sensor fails, the refrigerator begins to behave “inappropriately”. Here main symptomsthat should alert you:

• ❄️ The refrigerator does not turn off. The compressor works constantly, it freezes too much, the food is covered with ice;
• 🔥 The refrigerator does not cool. The compressor does not turn on, the chamber is warm, the food is spoiling;
• 🌡️ The temperature fluctuates. It is either too cold or too warm, despite the settings;
• ⚡ Frequent clicks of the relay. The refrigerator tries to start, but immediately turns off (a sign of an open circuit in the sensor circuit);
• 🚨 Error on the display. Modern models (Samsung, LG) show fault codes, for example, E1, FF or OF.

However, these same symptoms may indicate other problems:

• Failure of the compressor;
• Freon leak;
• Failure of the control board;
• Clogged capillary tube.

How to distinguish a sensor malfunction from other failures?

⚠️ Attention: If the refrigerator is electronically controlled (Samsung, LG, Bosch) shows an error, do not try to reset it by turning it on/off repeatedly. This may lead to blocking of the board. It is better to immediately disconnect the refrigerator from the network and call a technician.

How to check the temperature sensor yourself

If you suspect, that the problem is in the sensor, you can check it at home. To do this you will need:

• 🔧 Multimeter (to measure resistance);
• 🧊 A glass of cold water and ice;
• 🔥 Hair dryer or warm water (to heat the sensor);
• 📄 Documentation for the refrigerator (to find out the nominal resistance of the sensor).

Testing instructions:

1. Disconnect the refrigerator from the power supply. This is mandatory for safety!
2. Remove the protective panel. In most models, the sensor is located on the back wall of the refrigerator compartment.
3. Disconnect the sensor connector. Usually this is a two-pin connector with a latch.
4. Measure the resistance.
   • Connect the multimeter probes to the contacts sensor;
   • Record the readings at room temperature (~20°C);
   • Immerse the sensor in a glass of cold water (0°C) and measure the resistance again;
   • Heat the sensor with a hair dryer (no higher than 50°C!) and repeat the measurement.

Compare with the nominal values. For NTC thermistor the resistance should:

• Decrease when heated;
• Increase with cooling.

Example of normal values for a sensor NTC (may vary depending on the model!):

• At 20°C: ~5–10 kOhm;
• At 0°C: ~20–30 kOhm;
• At -20°C: ~50–100 kOhm.

If the resistance:

• Does not change with temperature changes → sensor is faulty;
• Equal to 0 or ∞ (break) → sensor is broken;
• Very different from the nominal value → replacement is required.

⚠️ Attention: In refrigerators with a system No Frost the defrost sensor is checked in the same way, but its nominal resistance may differ. For example, in Samsung RL38*** it is ~1. kOhm at 0°C.

How to replace the temperature sensor with your own hands

If the check shows that the sensor is faulty, you can replace it yourself. The main thing is to select a similar model and follow safety precautions.

What you will need:

• 🔧 New sensor (buy according to the part number from the documentation);
• 🔨 Screwdriver (Phillips or flathead);
• 🔌 Soldering iron (if you need to replace the connector);
• 🧲 Magnet or tape (to temporarily secure the sensor).

Step-by-step instructions:

1. Disconnect the refrigerator from the network. Let it stand for 10-15 minutes so that the capacitors discharge.
2. Remove the protective panel. In refrigerators Atlant or Indesit it is usually attached to clips, in Samsung —on screws.
3. Disconnect the old sensor.
   • Carefully snap off the connector;
   • If the sensor is glued, pry it flat a screwdriver;
   • Pull the sensor out of the mount.
4. Install a new sensor.
   • Insert it into the same mount;
   • Connect the connector (make sure the contacts are not oxidized);
   • Fix the panel back.

Check the operation of the refrigerator.

• Plug it in;
• Set the average temperature (+4°C);
• Check whether the compressor turns on and off after 10–20 minutes.

The cost of a new sensor depends on the refrigerator model:

• For Atlant or Biryusa: 300–800 ₽;
• For Samsung or LG: 1 000–2 500 ₽;
• For Bosch or Liebert: 2 000–5 000 ₽.

⚠️ Attention: In refrigerators with electronic control (Samsung, LG) after replacing the sensor, you may need to reset errors through the service menu. To do this, you need to press a certain combination of buttons (indicated in the service menu). manual).

How to find the part number of the sensor?

It is indicated on a sticker inside the refrigerator (usually on the side wall) or in the documentation. You can also remove the old sensor and read the markings on its body.

Frequently asked questions. temperature sensors

Is it possible to repair the temperature sensor or just replace it?

Temperature sensors (especially electronic ones) cannot be repaired. They can only be replaced with new ones. The exception is mechanical thermostats, where sometimes cleaning the contacts or replacing the gas helps (but this is a temporary solution).

How often do sensors break down? refrigerators?

The service life of the sensor depends on the type:

• Mechanical thermostats last 5–10 years;
• Electronic thermistors - 10-15 years;
• Digital sensors - up to 20 years.

Most often they fail due to surges voltage, corrosion of contacts or mechanical damage.

Why does the refrigerator freeze too much, even if the sensor is working?

If the sensor is checked and works normally, the reasons may be:

• Failure of the control board (gives incorrect commands);
• Clogged capillary tube (freon does not circulate normally);
• Compressor breakdown (works without stopping);
• Incorrect settings (for example, the mode is turned on Super Freeze).

Is it possible to use a refrigerator without a temperature sensor?

Technically it is possible, but this is highly not recommended. Without a sensor the compressor will either work constantly (risk of overheating) or not turn on at all. In modern models, the control board will simply block operation if there is no signal from the sensor.

How to protect the sensor from damage?

To extend the life of the sensor:

• Use a voltage stabilizer (electricity surges are the main reason). breakdowns);
• Do not drop or hit the refrigerator (sensors are sensitive to vibrations);
• Defrost the refrigerator regularly (ice and condensation can damage the contacts);
• Do not place the refrigerator near heat sources (radiators, stoves).