Brand refrigerators Liebherr are deservedly considered the standard of reliability in the world of climate control technology, but even the most advanced mechanisms are subject to wear. One of the key elements of the temperature control system is evaporator sensorwhich controls the temperature of the cooling element and regulates defrost cycles. When this component fails, the equipment no longer correctly maintains the microclimate, which can lead to food spoilage or the formation of excessive ice.
Understanding where exactly this sensor is located is necessary not only for diagnosing faults, but also for carrying out qualified maintenance. In models with the system NoFrost the sensor is hidden deep inside the structure, which requires partial disassembly of the unit to access it. The owner must be clearly aware that incorrect location of the element can lead to damage to the fragile evaporator or a violation of the tightness of the circuit.
In this article we will analyze in detail the architecture of refrigeration chambers Liebherr, indicate the exact location of temperature sensors in various modifications and describe the algorithm of actions when replacing them. Diagnostic accuracy directly affects the service life of the compressor and the efficiency of the entire cooling system, so it is strictly not recommended to ignore the malfunction signals of this unit.
The principle of operation and the role of the sensor in the NoFrost system
System NoFrost v refrigerators Liebherr is built on forced air circulation and periodic automatic defrosting of the evaporator. The central element of this process is the defrost sensor, which records the temperature on the surface of the evaporator core. While the temperature is below the set threshold (usually about -10°C...-15°C), the sensor has a high resistance and gives a command to the controller to operate the compressor.
When the defrosting cycle begins, it turns on Defrost heating elementand the sensor continues to monitor heating. As soon as the evaporator temperature reaches a positive value (usually +10°C...+15°C), the sensor resistance drops sharply. This serves as a signal to the electronic module that the ice has melted and the heating element must be turned off so as not to overheat the system and waste energy.
If the evaporator sensor is faulty, two scenarios are possible. In the first case, the system “thinks” that there is no ice and does not turn on defrosting, which leads to a “coat” of fouling on the evaporator and the cessation of air circulation. In the second case, the sensor can constantly signal the need for defrosting, forcing the heating element to work continuously, which is dangerous due to overheating of plastic parts and the risk of fire.
⚠️ Attention: Operating a refrigerator with a faulty defrost sensor in the “constant defrosting” mode can lead to melting of the plastic housing of the evaporation unit and damage to the wiring.
Modern models Liebherr equipped with self-diagnosis, which reacts to abnormal sensor readings. Error codes may appear on the display indicating an open circuit or short circuit in the sensor circuit. Understanding the principle of operation helps to quickly determine whether the problem lies in the sensor itself or in the control unit.
Localization of the sensor in Liebherr NoFrost refrigerators
The search for the evaporator sensor in refrigerators Liebherr with a full defrost system NoFrost always begins from the freezer. This is where the main evaporative unit is located, hidden behind the rear panel. Unlike drip systems, where sensors can be publicly accessible on the rear wall, dismantling of internal elements is required here.
The evaporator temperature sensor (often marked as B6 or Evaporator Sensor) is physically attached directly to the aluminum fins of the radiator or inserted into a special technological hole in the evaporator housing. Its task is to read the temperature of the metal as accurately as possible, so it is always in direct contact with the heat exchanger, often fixed with a plastic bracket or aluminum tape for better heat transfer.
Access to the sensor location area is blocked by a plastic cover, which also serves as an air duct. In some models of the series CBN or ICBN this panel can be combined with a decorative insert or drawer holder. To gain access, you must carefully remove all fasteners without using excessive force, since the plastic becomes very fragile in the cold.
It is important to distinguish between the evaporator sensor and the air sensor. The first is located “inside” the cooling system (behind the wall), the second is in the working chamber, often in the upper part or in a special box. Confusion in terms can lead to the diagnosis of a serviceable element while the real culprit of the malfunction remains hidden.
Access to the sensor in models with full defrosting (LowFrost)
In refrigerators Liebherrusing technology LowFrost or partial defrosting, design evaporator may differ. Here the evaporator is often built into the chamber walls or located behind a removable panel, which does not require complete dismantling of the inner lining. The sensor in such models is also attached to the surface of the evaporator, but it is somewhat easier to get to.
In two-chamber models with one compressor and a crying evaporator in the refrigerator compartment, there may be no defrost sensor at all, since defrosting occurs naturally when the compressor is turned off. However, if we are talking about a freezer compartment with manual or semi-automatic defrosting, an overheating sensor (thermal fuse) can be installed next to the heating element for safety.
To visualize the location of elements in different types of systems, let's look at the comparison table:
| System type | Location evaporator | Access to the sensor | Replacement frequency |
|---|---|---|---|
| NoFrost | Hidden behind the back panel of the freezer | Complicated (disassembly required) | Rarely (5-7 years) |
| LowFrost | Built into the walls or behind the panel | Medium (removable panel) | Average (4-6 years) |
| Static (Drip) | On the back wall of the refrigerator cameras | Open (visible immediately) | Rarely |
When working with models LowFrost you should be especially careful when removing the back panel, since refrigerant pipes may be connected to it. Damage to the circuit at home cannot be repaired without special equipment.
Instructions for dismantling the rear panel and finding the sensor
The process of gaining access to the evaporator sensor in refrigerators Liebherr requires sequential operations. Failure to do so may result in broken plastic latches or damaged wiring. Below is the algorithm for most models of the series Comfort and Premium with the system NoFrost.
First, you must completely empty the freezer of food, shelves and drawers. Pay special attention to the top drawer and guides, which often interfere with panel removal. After this, the screws securing the back wall are unscrewed. In some models, the screws may be hidden under decorative plugs or located inside niches for drawers.
☑️ Algorithm for accessing the sensor
After removing the panel, you will have a view of the evaporator - an aluminum radiator with wound copper tubes. The sensor is usually located in the lower or middle part of this radiator. It is a small metal or plastic cylinder from which two wires extend into the wiring harness. Fastening can be done with a clip or pressed into the housing.
If a thick layer of ice is visible on the evaporator, do not try to chip it with a knife or sharp objects. Use a hair dryer (on low heat) or just let the ice melt naturally. Mechanical impact on the evaporator fins is guaranteed to lead to freon leakage.
⚠️ Attention: Plastic guides and panel latches become brittle at low temperatures. Warm them up with a hair dryer before dismantling them to avoid cracks.
Diagnostics and checking the serviceability of the sensor
Before proceeding with replacement, you need to make sure that it is temperature sensorthat has failed, and not the control module or heating element. For diagnostics, you will need a multimeter configured to measure resistance (Ohms). Sensors Liebherr most often have a negative temperature coefficient of resistance (NTC), that is, when heated, their resistance drops.
The verification process consists of measuring the resistance of the sensor at room temperature and comparing the readings with reference values. For standard sensors Liebherr at a temperature of +20°C, the resistance is usually about 10-12 kOhm (values may vary depending on the specific model and series of the sensor). When the sensor cools (for example, in a glass of water and ice), the resistance should increase.
If the multimeter shows an “open circuit” (infinity) or a “short circuit” (zero), the sensor is clearly faulty. Also a sign of a malfunction is the absence of a change in resistance readings when the temperature of the sensor changes. In some cases, the sensor may produce plausible values, but have a nonlinear characteristic, which confuses the controller's operating algorithm.
Table of approximate resistance values for Liebherr sensors
At +25°C, the resistance is approximately 8-10 kOhm. At 0°C the resistance increases to 25-30 kOhm. At -18°C the resistance can reach 60-70 kOhm. The exact values depend on the sensor part number indicated on its body or in the service documentation.
It is important to check not only the sensor itself, but also the integrity of the wires leading from it to the connector. Often the wire breaks at the point of entry into the sensor housing or in the area where it passes through the door hinge (if the sensor is a door, but the principle is the same). Continuity of the circuit from the connector to the end of the wire will help to eliminate a break in the route.
Replacement of the sensor and assembly of the system
Replacement of the evaporator sensor in the refrigerator Liebherr is carried out with an element of similar characteristics. Using universal sensors without selecting the resistance value can lead to incorrect operation of the defrost system. Original spare parts are marked according to a specific series of refrigerators.
To replace, you must disconnect the sensor connector from the wiring harness. If the connector is soldered or twisted, the connection is pulled apart neatly. The new sensor is installed in place of the old one, ensuring tight contact with the surface of the evaporator. To improve thermal contact, thermal paste is sometimes used, although in the factory, a simple tight fit into the hole is often used.
The connection of the wires must be reliable and insulated. It is best to use soldering followed by insulation with a heat-shrinkable tube, since the twists may oxidize or come apart under conditions of vibration and temperature changes. After installing the sensor, reassembly is performed: installing the back panel, drawers and shelves.
After assembly, the refrigerator is connected to the network. The first cycle of work may take several hours. It is recommended to monitor the occurrence of defrost cycles (the sound of dripping water is heard or the click of the heating element shutdown relay) in the first 24 hours of operation. If the system is working properly, ice will not form on the evaporator.
Frequent maintenance errors and fault codes
When doing self-repair, owners often make mistakes that aggravate the situation. One of the most common is ignoring complete defrosting before disassembling. An attempt to remove a panel with frozen ice leads to breaking off the fasteners and damaging the evaporator fins. Polarity is also often confused when connecting (although for most NTC sensors this is not critical, it can be fatal for digital sensors).
Refrigerators Liebherr display information about faults in the form of error codes on the display or by blinking indicators. For example, a flashing temperature segment or an "F" symbol may indicate problems in the freezer related to the sensors. Codes may vary depending on the generation of electronics (E1, E2, F5, etc.).
The following is a list of typical symptoms indicating problems with the evaporator sensor:
- ❄️ A thick layer of ice or snow has formed on the back wall of the freezer, although this has not previously been observed.
- 🔊 The compressor works non-stop, trying to gain temperature, but there is not enough cold in the chamber.
- 💧 There is water at the bottom of the refrigerator or under the drawers, which does not have time to evaporate due to frequent defrosting.
- 🔥 There is a smell of halogen or burnt wiring in the area of the freezer compartment (if the heating element is stuck).
If the problem persists after replacing the sensor, the control module itself may be faulty or there are problems with the defrost heating element. In such cases, more in-depth diagnostics are required using the service menu or an oscilloscope.
Is it possible to temporarily operate a refrigerator with a faulty sensor?
Operation is possible only in emergency mode with constant monitoring. If the sensor “lies” in the direction of cold, the refrigerator will work continuously, which will lead to freezing and eventual breakdown of the compressor. If the sensor shows heat, the heating element may turn on and melt the plastic. It is recommended not to store valuable products and call a specialist.
Where to buy an original sensor for Liebherr?
It is better to purchase original spare parts from official dealers Liebherr or in specialized stores of spare parts for household appliances, indicating the exact model of the refrigerator (number on the nameplate). Universal sensors may not fit the calibration curve.
Why does the refrigerator not freeze after replacing the sensor?
There may be several reasons: the sensor rating is incorrectly selected, poor contact in the connector, damage to the wires during installation or the presence of another malfunction (freon leak, compressor failure) that was disguised as a sensor problem.
How often do you need to change the evaporator sensor?
The service life of the sensor is usually 5-10 years. No scheduled replacement is required; it is replaced only when it fails. However, if the refrigerator operates in extreme conditions (voltage surges, high humidity), the resource may be reduced.