Refrigerators Liebherr deservedly considered one of the most reliable in their class, however, even German precision sometimes fails in the form of incorrect temperature conditions. Often the cause is a failure or incorrect operation temperature sensor, which is the “eyes” of the electronic control system. Understanding where exactly this sensitive element is located is necessary for carrying out initial diagnostics or replacing the part.
In this article we will analyze in detail the architecture of the cooling system of various models, from classic two-chamber devices to complex systems NoFrost i DuoCooling. You will learn how to get to the sensor, what tools are needed and what to look for when visually inspecting the wiring. It is critically important to know the exact location of the sensor, since in some models there can be up to four of them, and each is responsible for its own circuit.
Before you begin disassembling, you need to protect yourself and the equipment. Disconnect the unit from the power supply by removing the plug from the socket. Any manipulation of live electronics may result in irreversible damage to the control board or injury. Next, we will look at the main components where temperature sensors are hidden.
The principle of operation of temperature sensors in the Liebherr system
Modern refrigerators Liebherr are controlled by complex electronics that rely on the readings of thermistors. These elements change their electrical resistance depending on the ambient temperature. Thermal sensor does not measure temperature directly, like a mercury thermometer, it only transmits resistance, which the processor converts into digital values.
Most models use an NTC thermistor (Negative Temperature Coefficient). This means that as the temperature rises, its resistance decreases, and as it cools, it increases. The control system reads these fluctuations and makes a decision to turn on or off the compressor, fans or defrost heating elements. If the data from the sensor falls outside the acceptable range, a corresponding error appears on the display.
The accuracy of the readings directly affects the shelf life of products and energy consumption. A misaligned or faulty sensor can cause the compressor to work non-stop, which will lead to freezing of the contents and rapid wear of the motor. Therefore, timely diagnosis of these elements is the key to the long service of your Liebherr.
Location of sensors in the refrigerator compartment
In the refrigerator compartment, sensors are usually located in areas where air circulation is most representative of the entire volume. In models with a drip defrost system (Cooling), the sensor is often hidden behind a plastic panel on the back wall. You can get to it by carefully snapping off the fasteners or unscrewing the screws hidden under the decorative plugs.
If your refrigerator is equipped with a system NoFrost or FrostSafe, then there may be a sensor in the refrigerator compartment that controls the temperature of the evaporator to prevent the formation of an ice crust on food. It can be built into the duct or mounted on the wall of the cold air supply duct. Some advanced models Liebherr use technology DuoCoolingwhere each circuit has its own independent sensor.
To access these elements, it is often necessary to remove shelves, drawers and side guides. Be careful with plastic clips - they can be fragile, especially if the plastic has been exposed to temperature changes for a long time. It is recommended to use a special tool to open the panels so as not to damage the case.
☑️ Preparing to search for the sensor in the refrigerator compartment
Visually, the sensor is a small metal or plastic cylinder from which wiring comes. Wires can be protected by corrugation or built into bundles. It is important not to damage the insulation during inspection, as this may lead to false readings.
Looking for sensors in the freezer and NoFrost system
The freezer is the area with the most extreme conditions, and this is where the largest number of control elements are located. In systems NoFrost defrost sensors are critical. They are located directly on evaporator, which is hidden behind the back panel of the freezer. To get to them, it is necessary to completely dismantle the inner lining of the chamber.
The defrost sensor is usually attached to the evaporator tubes or inserted into a special socket on aluminum fins. Its job is to signal the control board when a certain temperature has been reached during the defrost cycle. If this element fails, the refrigerator may either not start defrosting (which will lead to ice accumulation) or heat the evaporator for too long.
Also, the freezer may contain a main temperature sensor that regulates the operation of the compressor. In two-compressor models, it is responsible only for the freezer. In single-compressor systems NoFrost control can be carried out using the freezer chamber sensor, and the damper in the refrigerator compartment opens as needed.
⚠️ Attention: When removing the rear panel of the freezer, be extremely careful. Ice crust, if present, can damage the aluminum evaporator tubes or sensor wiring. Do not use sharp metal objects to chip ice.
Often the sensors in the freezer Liebherr are connected in a single circuit with defrosting heating elements. When replacing one element, it is recommended to check the resistance of the entire circuit. Oxidation of contacts in this unit is a common cause of problems.
Hidden self-diagnosis function
In many Liebherr models, when connected to the network or through a certain combination of buttons, you can run a sensor test. The screen can flash or show the current sensor resistance values, which allows you to find the faulty element without disassembling.
Location table of the main sensors by model
Different series of refrigerators Liebherr have different layouts. Below is a summary table to help you figure out where to look for the main sensor depending on the type of device. Remember that modifications may vary, and it is always better to check the exact location with the diagram in the service documentation.
| System type | Main sensor (MC) | Defrost sensor (MK) | Additional sensor |
|---|---|---|---|
| Static (Drip) | On the back wall, inside the chamber | Absent (manual/automatic defrosting) | Possibly in the control unit |
| NoFrost (Single compressor) | Air duct between the chambers | On the evaporator (behind the rear wall of the MK) | Air temperature control |
| DuoCooling (Two circuits) | Inside the fridge compartment | Inside the freezer compartment | BioFresh fresh zone sensor |
| VarioCooling | In the storage area | On the evaporator | SuperCool zone sensor |
As can be seen from the table, the complexity of the design directly affects the number of sensors. In simple models there may be only one or two, while in premium series with a zone BioFresh the number of sensors increases to accurately maintain the microclimate in each drawer.
If you are looking for a sensor for a specific model, for example Liebherr CNP 3713 or IKB 3550, pay attention to marking on the nameplate inside the camera. By product number (Product No.) you can find the exact explosion diagram (exploded view) on the manufacturer’s official website, where each node is numbered.
Fault symptoms and error codes
You can understand that the problem lies in the temperature sensor by its characteristic signs. The most obvious is the constant operation of the compressor without shutdowns or, conversely, too infrequent activation, leading to defrosting of food. Also, the refrigerator may hum louder than usual due to continuous operation.
Electronics Liebherr can diagnose an open or short circuit in the sensor circuit. In this case, the alarm indicator (red triangle or exclamation mark) lights up on the display, and if there is an alphanumeric display, an error code is displayed. The most common codes associated with temperature sensors:
- 🔴 F1 — Malfunction of the temperature sensor in the refrigerator compartment (break or short circuit).
- 🔴 F2 — Problem with the sensor in the freezer compartment.
- 🔴 F3 — Error in the defrost sensor (evaporator).
- 🔴 F4 — Sensor malfunction in the zone BioFresh (if applicable).
Sometimes the error can be floating. For example, the sensor “lies” at certain temperatures, but shows the norm at others. In such cases, diagnostics with a multimeter is mandatory. It is necessary to ring the sensor at room temperature and compare the readings with reference values for NTC thermistors (usually about 6-10 kOhm at +20°C, but the exact numbers depend on the model).
⚠️ Attention: Resetting the error by disconnecting the refrigerator from the network for 15 minutes only helps if it was caused by a power surge. If the sensor is physically faulty, the error will return immediately after starting the cooling cycle.
Replacement process and important nuances
Replacing the temperature sensor in the refrigerator Liebherr is a procedure that requires care. Once you have reached the faulty element, it must be disconnected. Often the connectors are located in hard-to-reach places, behind insulation. In some models, the sensor wires are pressed into the polyurethane foam insulation of the case, which requires extremely careful cutting.
The new sensor must have exactly the same resistance and geometric dimensions. Using analogues with other characteristics will lead to incorrect operation of the entire system. When installing a new element, use thermal paste (if the sensor is inserted into a metal sleeve) to improve heat transfer.
After assembling and connecting the refrigerator to the network, the system may require time (up to 24 hours) to stabilize the temperature and calibrate. Do not load the chamber with products immediately, let the equipment enter the operating cycle.
If you are not confident in your abilities, especially in matters of working with electrical circuits and refrigerant (at the risk of damaging the evaporator), it is better to contact an authorized service center. Unprofessional disassembly may void the warranty or damage expensive components.
Is it possible to temporarily short-circuit the sensor to make the refrigerator work?
Technically, shorting or installing a fixed resistor can force the compressor to turn on. However, this is extremely dangerous: the refrigerator will stop regulating the temperature, which will lead either to defrosting of the food or to freezing of the evaporator and failure of the compressor. This solution is only for short-term diagnostics, but not for operation.
Why does the error not disappear after replacing the sensor?
Perhaps the new sensor is also faulty or has inappropriate parameters. The second reason is that the problem is not in the sensor itself, but in the wiring (breakage, oxidation of contacts) or in the control board, which does not read the readings correctly. You may also need to reset errors through the service menu.
Where to buy an original sensor for Liebherr?
It is best to look for original spare parts by the Product No. of your refrigerator in official spare parts stores or from authorized partners Liebherr. The use of cheap Chinese analogues often leads to repeated breakdowns after a short period of time.