Sudden spoilage of food or the appearance of a characteristic error code on the display of a modern refrigerator Bosch often signals a failure of one of the key elements of the control system - the temperature sensor. This small component is responsible for controlling the climate inside the chambers, and its incorrect operation can lead to icing of the evaporator or, conversely, to insufficient cooling. Understanding the principle of operation and the ability to replace thermistor on your own allows you to save a significant amount on calling a technician and quickly bring the equipment back to life.
Owners often ignore the first signs of a malfunction, such as frequent switching on of the compressor or the appearance of condensation on the walls, which ultimately leads to more complex repairs. Replacing the sensor in refrigerators Bosch is a procedure accessible to a person with minimal skills in handling tools, if you act strictly according to the instructions and follow safety precautions.
In this article we will analyze in detail the process of diagnostics, selection of compatible spare parts and step-by-step replacement of the sensor in various models of refrigerators Bosch. You will learn how to correctly interpret multimeter readings and what to pay attention to when installing a new element in order to avoid repeated breakdowns.
Symptoms of malfunction and diagnostics of a temperature sensor
The first sign that thermal sensor has stopped reading the temperature correctly is the appearance of a blinking indication on the digital display temperature values. In refrigerators Bosch this is often accompanied by error codes, such as E1, E2 or F1, which indicate an open circuit or short circuit in a particular sensor. However, the self-diagnosis system does not always generate an error immediately; sometimes the refrigerator simply starts working in emergency mode, constantly driving the compressor.
For accurate diagnostics, you need to remove the sensor and check its resistance using a multimeter switched to resistance measurement mode (Ohm). A working thermistor at room temperature (about +25°C) should show a resistance in the range of 4 to 6 kOhm, although the exact values depend on the specific model and type of sensor. When the element cools (for example, if you hold it with your fingers or blow cold air), the resistance should increase smoothly.
⚠️ Attention: If the multimeter shows infinity (one in the most significant digit) or zero, the sensor is clearly faulty and requires replacement. Do not attempt to repair the sensor housing - it is a sealed element.
A frequent problem is not complete failure, but “drift” of readings when the sensor transmits incorrect data at a certain temperature. In this case, the refrigerator may not defrost properly or may overcool food. To check, you can place the sensor in a container with water of a certain temperature and take readings, comparing them with a reference table.
Necessary tools and preparation for repairs
Before you start disassembling the refrigerator panels Bosch, you need to prepare a workplace and a set of tools. You will need access to the rear and interior of the unit, so make room around the equipment. To carry out the replacement work temperature sensor you will need a minimum set of plumbing and measuring instruments.
The main tool will be a multimeter for initial diagnostics and testing of a new spare part. You will also need screwdrivers (Phillips and flat-head), needle-nose pliers for working with terminals, and possibly a knife for carefully stripping the insulation. Don't forget to prepare a container for defrosting if you need access to the evaporator, and a hairdryer to speed up the process of thawing the ice.
☑️ Tools for replacing the sensor
The critically important stage of preparation is complete disconnecting the refrigerator from the power supply. In models Bosch with the system No Frost electronic boards are located in accessible places, but the risk of electric shock or short circuit due to careless handling of wires always remains. Let the equipment stand turned off for at least 15-20 minutes before starting disassembly so that the capacitors on the control board are discharged.
The location of sensors in different Bosch models
The structural location of temperature sensors in refrigerators Bosch varies depending on the series and year of manufacture of the model. In most modern units with the system No Frost the main air sensor is located at the top of the refrigerator compartment, often hidden behind a decorative plastic panel or duct grille.
In two-chamber models, a second sensor usually monitors the temperature of the evaporator in the freezer. It can be located directly on the evaporator fins or built into a plastic casing next to the fan. In some modifications, such as series Bosch KGN, access to the freezer chamber sensor is possible only after complete disassembly of the rear wall of the freezer.
The defrost sensors, which are often confused with air temperature sensors, deserve special attention. The defrost sensor is responsible for turning the evaporator heating element on and off and is attached directly to the aluminum fins. An error in replacing these elements will result in the defrosting system not starting and the evaporator becoming overgrown with ice, blocking air circulation.
| Sensor type | Typical location | Function | Frequent error |
|---|---|---|---|
| Air sensor | Upper part of the refrigerator compartment | Compressor operation control | E1 / F1 |
| Evaporator sensor | Behind the rear wall of the freezer | Control of the defrost cycle | E2 / F2 |
| Defrost sensor | On the evaporator fins | Protection against overheating of the heating element | Defrost malfunction |
| Condenser sensor | Near the compressor (rarely) | System protection | Compressor shutdown |
Hidden installation in the Bosch KGN series
In some models of the KGN series, the air temperature sensor can be hidden inside the plastic duct of the air duct that comes from the fan. To gain access, you will need to carefully snap off the channel clamps without breaking the plastic, which becomes very fragile in the cold.
Step-by-step instructions for replacing the sensor
The replacement process begins with dismantling the plastic panels that block access to the insides of the refrigerator. In the refrigerator compartment Bosch usually it is necessary to remove the top shelf and unscrew the mounting screws that hold the rear decorative panel or duct. Proceed with caution as the plastic latches can be fragile.
Once you gain access, locate the old sensor - it is a small plastic cylinder with two wires going to a connector. Disconnect the connector from the wiring harness (sometimes it is hidden in a corrugation or clamped with a clip). If the sensor wires are soldered into the board or connected by twisting, they will have to be carefully cut, leaving a margin for connection to the new element.
⚠️ Attention: Never pull the sensor wires with force. The wiring in refrigerators Bosch is thin and can easily break inside the insulation, which will create a new problem with contact.
Install the new sensor in the same location, ensuring its tight contact with the measured medium (air or evaporator). Connect the wires of the new sensor to the refrigerator wiring. To connect, use high-quality soldering followed by insulation with a heat-shrinkable tube or twisting using special connecting sleeves. Ordinary electrical tape in conditions of low temperature and humidity may lose its properties over time.
After installation, reassemble the structure in reverse order, making sure that all wires are laid in their channels and do not fall under moving parts (for example, fan blades). Plug in the refrigerator and check its operation during the first hour.
Checking performance and calibration
After replacing thermistor and turning on the refrigerator Bosch it may take some time to reach operating mode. The electronic control unit must read new resistance readings and adjust the operation of the compressor. In most cases, calibration occurs automatically and no special actions are required from the user.
However, if the error code continues to appear on the display, try resetting the system. To do this, unplug the refrigerator for 10-15 minutes and then turn it on again. This action will reset the controller and it will run a new circuit diagnostic. If the error has disappeared, but the refrigerator does not work correctly (for example, it does not turn off), a sensor with an inappropriate resistance rating may be installed.
Check the tightness of the wire connections. A bad contact can simulate a sensor break, and the system will again generate an error. Make sure that the connection point is reliably insulated and protected from moisture, which inevitably forms during defrosting cycles.
Frequent errors during self-repair
One of the most common mistakes is installing a universal sensor without checking its temperature characteristics. Sensors Bosch can have different resistances at 25°C (for example, 5 kOhm, 10 kOhm or 13 kOhm). Installing the wrong element will cause the refrigerator to “think” that the temperature in the chamber has already been reached and will turn off the compressor too early, or will work non-stop.
The second common mistake is neglecting the insulation of connections. Moisture inside the refrigeration chamber is an aggressive environment for open copper twists. Oxidation of the contacts in a month or two will lead to repeated failure, and you will have to look for the cause again. Use only high-quality materials for insulation.
Also, novice technicians often forget to check the condition of the wiring itself going from the sensor to the board. In refrigerators No Frost wires can rub against the edges of plastic panels or break at bends due to vibration of the compressor. If you replace the sensor and the problem remains, “ring” the entire path of the wire to the connector on the control board.
⚠️ Attention: The characteristics of the sensors may differ even within the same refrigerator model, depending on the year of manufacture and the manufacturer. Always check the markings on the old sensor before purchasing a new one.
FAQ: Frequently Asked Questions
Is it possible to temporarily short-circuit the sensor wires to make the refrigerator work?
It is strictly not recommended. Shorting the wires (simulating very low temperatures) will cause the compressor to run continuously, which will lead to freezing of food in the refrigerator compartment and possible failure of the compressor due to overheating. This is an emergency measure for diagnostic purposes only, not for operation.
Where can I find the exact sensor markings for my Bosch model?
The markings are usually placed on the sensor body itself or on a tag attached to the wire next to the connector. Look for codes like 00623571, 00623572 or analogues. Also, the spare part number can be found in official catalogs Bosch by the full model number of the refrigerator (indicated on the nameplate inside the chamber).
Why does the new sensor not solve the problem with the error code?
There may be several reasons: the electronic control board itself is faulty (the resistor in the sensor circuit has burned out), the wiring between the sensor and board, or a sensor with the wrong resistance is installed. A “glitch” of the controller is also possible, requiring professional reprogramming.
Is it necessary to defrost the refrigerator before replacing the evaporator sensor?
Yes, if access to the sensor is blocked by ice or it is located on the evaporator. Working with plastic elements and wires in the presence of ice is dangerous - the plastic becomes brittle and breaks, and water can cause a short circuit when turned on. Allow the refrigerator to completely thaw before starting work.