When the refrigerator Liebherr stops cooling, and the compressor is either silent or makes only a short click and hum, the problem often lies in the engine starting system. Owners of premium equipment are faced with the need for quick diagnostics to prevent product spoilage. The key element that ensures the motor starts is start-protection relay, which is located directly on the compressor housing.
Finding this part may seem difficult due to the dense arrangement of the units in the rear niche of the refrigeration cabinet. However, understanding the design allows you to reduce repair time and avoid unnecessary costs of calling a technician. In this article, we will look in detail at where exactly to look for the relay, what it looks like in different models, and what nuances should be taken into account when replacing it yourself.
It is worth noting right away that in modern models Liebherr with inverter compressors, the starting system may differ from classical circuits. Instead of a mechanical relay, an electronic control module is often used here, integrated into a common board or mounted next to the motor. The exact location depends on the series of the refrigerator: in classic models the relay is mounted on the compressor shank, in inverter models it is a separate unit or part of the electronics.
Functional purpose and principle of operation
The starting relay performs a critical task: it supplies increased current to the compressor starting winding at the moment of switching on, helping the rotor overcome inertia and begin rotating. Without this element, the engine would only hum, heating up, but would not start. In parallel with the starting function, the device is often combined with thermal protection relaywhich opens the circuit when the windings are overheated or overcurrent.
The principle of operation of a mechanical relay, which is most often found in classic models. Liebherr, based on electromagnetic induction. When voltage is applied, current passes through the coil, creating a magnetic field that draws in the core and closes the contacts of the starting winding. As soon as the rotor picks up speed, the current drops, the magnetic field weakens, and the contacts open under the influence of gravity or a spring.
⚠️ Attempting to start the compressor without a working relay or with shorted contacts will burn out the motor starting winding in a matter of seconds. This is irreversible damage that requires replacement of the entire compressor.
In electronic versions, typical of newer lines, the relay function is performed by a solid-state element or microcircuit. They have no moving parts and are considered more reliable, but require accurate diagnostics with a multimeter or oscilloscope to check the control signal.
Location of relays in different Liebherr series
The location of the starting device depends on the year of manufacture and the type of compressor installed. In most classic models of refrigerators Liebherrsuch as the series CT, CU, CN and CBN old model, the relay is located at the bottom of the unit. To get to it, you need to remove the rear metal or plastic cover covering the compressor compartment.
After removing the cover, you will see a black cylindrical or pear-shaped compressor tank. The relay is always mounted on the side or bottom end of the motor rod. It is a plastic box of black or white color, to which electrical wires fit. In models with two compressors (separately for the refrigerator and freezer compartments), the relays will be located on each motor respectively.
In modern models with a system NoFrost and inverter motors, the design may be different. Here the relay can be placed in a separate control unit located on the wall of the compressor compartment, or integrated into the frequency converter board. In such cases, a visual search for a small hinged element on the compressor may not yield results, since it is not physically present in its usual form.
To accurately determine the type of your unit, you should check the technical documentation or the sticker on the case. The serial number indicated in the device passport allows technicians to determine the exact configuration of the electrical circuit. If there is a massive black block with a radiator hanging on the compressor, most likely you have an inverter system, where relay diagnostics require a professional approach.
Visual identification and types of devices
Start relay Liebherr
may have a different appearance depending on from the component manufacturer (parts Secop, Danfoss or original marked blocks are often used). A classic electromagnetic relay usually has a rectangular or cubic shape with a hole for mounting on the compressor rod. Technical specifications, such as voltage and maximum current, are often stamped on the case.Thermal protection is often built into the same housing or mounted on top of it in the form a separate “pill” or cap with two contacts. It is important to distinguish between these elements, since in the event of a malfunction, sometimes only the thermal protection needs to be changed, and sometimes the entire assembly. On older models, relays could be ceramic, which provided them with a long service life, but modern analogues are made of heat-resistant plastic.
Below is a table that helps identify the type of relay by external signs and symptoms:
| Relay type | Appearance | Characteristic sound of a malfunction | Contact location |
|---|---|---|---|
| Electromagnetic | Plastic box, coil and core inside | Loud click, then buzzing | Vertical or horizontal |
| Thermal (protection) | Metal or plastic cap | No sound, cold compressor | At the end of the relay housing |
| Posistor | Small cylinder inside the case | Silence or rare clicks | Inside the main unit |
| Electronic | Board with microcircuits or black block | Electronics squeak or silence | Separate module |
When inspecting, pay attention to the condition of the contacts. If carbon deposits, melted plastic, or a burning smell are visible inside the relay, the part requires immediate replacement. Even if there are no visual defects, mechanical wear of the moving parts could disrupt the switching.
Instructions for dismantling and replacement
Before starting any work on repairing the electrical equipment of the refrigerator Liebherr it is necessary to completely de-energize the device. Unplug the power cord from the outlet and make sure there is no voltage in the compressor compartment. This is a basic safety rule, ignoring which may result in electric shock.
The replacement process begins by removing the protective cover of the compressor compartment. It is usually secured with bolts or snaps. Once you have access, locate the compressor and the relay located on it. Carefully remove the retaining bracket or spring clip that holds the relay to the motor stem. Do not use excessive force to avoid damaging the tubes or wires.
☑️ Preparing to replace the relay
Remove the relay from the rod by pulling it down or to the side, depending on the design. Disconnect the electrical terminals. It is recommended to first take a photo of the connection diagram so that when installing a new part you do not mix up the wires. The new part is installed in the reverse order: first the wires are connected, then the relay is put on the rod until a characteristic click is heard and secured with a clamp.
⚠️ Attention: When installing a new relay, make sure that it is oriented correctly. The housing often has a marking UP or an arrow indicating the top position. Incorrect installation will result in the mechanism not working.
After assembly, do not rush to close the lid. Plug in the refrigerator and listen to the compressor work. If you hear a confident start and a subsequent even hum, and after a while the coldness in the chambers begins to increase, it means that the replacement was successful. If the compressor hums and stops after a few seconds, the problem may be deeper.
Diagnosing faults with a multimeter
Before buying a new part, it makes sense to check the old one, especially if it looks intact. To do this, you will need a household multimeter switched to continuity or resistance measurement mode. The removed relay must be carefully opened (if the design allows) or ring through the contact groups.
The electromagnetic coil is checked by measuring the resistance between the corresponding contacts. It should be low, usually within a few ohms. If the device shows infinity (open) or zero (short circuit), the coil is faulty. The thermal relay is checked for current flow: in a cold state it should ring, and when heated (which is difficult to check at home without special equipment), open the circuit.
Nuances of checking a posistor
Inside many modern relays there is a posistor - a ceramic element that changes resistance when heated. When cold it has low resistance. If the multimeter shows an open circuit, the posistor has burned out and the relay will not start the compressor. Warming it up with a hairdryer can temporarily restore its operation, but this will only confirm the diagnosis: the part must be replaced.
It is also worth checking the contacts for oxidation. Even a thin layer of oxide can prevent the inrush current from passing through. Cleaning the contacts with fine sandpaper sometimes helps to revive the relay, but this is a temporary measure. For reliable operation of the refrigerator Liebherr it is better to use new components.
Frequent errors and precautions
One of the common mistakes is trying to install a relay from another model or manufacturer without taking into account the characteristics. Although the seats may be the same, the cut-off current parameters and response time may differ. This will either lead to the compressor not starting or to its rapid failure.
Another mistake is ignoring the condition of the compressor itself. If a relay burns out, this is often a consequence, not a cause. For example, a jammed compressor or an interturn short circuit causes an overload, which the relay tries to compensate for until it burns itself out. Replacing the relay in this case will only give a short-term effect.
Do not forget about cleanliness in the compressor compartment. Dust, animal hair and cobwebs that accumulate over the years impair heat dissipation and can cause electrical contacts to overheat. Regular cleaning of this area extends the life not only of the relay, but also of the entire refrigeration unit.
When you need to call a technician
Despite the apparent simplicity of replacing the relay, there are situations when independent repair is impractical or dangerous. If after replacing a part the refrigerator still does not start, the problem may lie in the compressor itself, the control board or wiring. Diagnostics of these units requires special equipment and knowledge.
It is also worth contacting professionals if you find a refrigerant leak (oily stains around the tubes, smell) or if soldering of the tubes is required. Interfering with the refrigeration circuit without a license and a vacuum pump is prohibited and will lead to complete breakdown of the equipment. Liebherr.
A qualified specialist will be able to conduct a complete diagnosis, check the current consumption of the motor and make sure the system is tight. This ensures that the repair will last and the food in your refrigerator will remain safe. Remember that saving on diagnostics can lead to the purchase of an expensive compressor to replace a burnt one.
Is it possible to use a relay from another refrigerator?
The use of analogues is possible, but only if the electrical characteristics (current, voltage) and mounting dimensions are the same. It is better to look for original spare parts Liebherr or certified analogues from Secop/Danfoss with the appropriate code.
Why does the relay burn out constantly?
Frequent burning of the relay indicates a problem with the compressor (difficult start, jamming) or power surges in the network. In such cases, it is recommended to install a voltage stabilizer and check the condition of the motor windings.
How long does the starting relay last?
The average service life of a mechanical relay is 5-7 years of active operation. However, if there are frequent voltage fluctuations or overheating of the compressor, it may fail much earlier.
Is it dangerous to change the relay yourself?
The replacement process is safe if the refrigerator is unplugged. The main danger is electric shock when the power is on or damage to the compressor tubes due to careless removal of the clamps.