A sudden stop of the refrigerator is often accompanied by a characteristic click, after which the motor hums, but cannot start, or is silent at all. In most cases, the culprit of such a breakdown is starting relay a small but critical element of the compressor electrical circuit. It is this unit that is responsible for supplying a starting pulse to the motor winding, allowing it to overcome the inertia of rest and start working.
Independent replacement of this part is one of the most common and economically justified types refrigerator repair. However, when going to a store or ordering a spare part online, it is easy to make a mistake, since outwardly similar cases can hide completely different internal mechanisms and electrical parameters. An incorrectly selected relay will not only not start the motor, but can also lead to overheating of the windings and failure of the compressor itself.
In this article we will look at how to correctly identify a faulty element, understand the complex markings of manufacturers and choose a reliable replacement. You will learn how modern posistor models differ from classic induction models, and what nuances to pay attention to during installation so that the equipment will last for many years.
Types of starting relays: principle of operation and differences
The first thing you will encounter when looking for a replacement is determining the type of device. Modern and old refrigerators use two main types of starters, which are not always interchangeable. Understanding their design will help you avoid a fatal mistake when purchasing.
The most common type today is PTC relay (posistor). Inside the plastic case there is a ceramic element, which, when voltage is applied, sharply changes its resistance. When cold, it conducts current, starting the engine, and then heats up and blocks the starting winding, putting the motor into operating mode. Such devices are often called “tablets” because of the shape of the main element.
The second type is induction (electromagnetic) relay. Inside it there is a coil and a movable core with contacts. When starting, the current in the coil creates a magnetic field that draws in the core and closes the contacts of the starting winding. When the motor accelerates, the current drops, the spring returns the core, and the circuit opens. These models are more sensitive to the installation position and often have markings indicating the permissible angle of inclination.
⚠️ Attention: It is strictly forbidden to install an induction relay instead of a PTC or vice versa, unless this is provided for by the versatility of a particular model. Different operating logic can lead to the fact that the starting winding remains on constantly, which will cause the compressor to burn out in a matter of minutes.
There are also universal kits that are suitable for a wide range of engines, but their use requires careful checking of current compatibility. Original spare parts are always preferable, since their parameters are ideally matched to a specific motor.
Marking and decoding of manufacturer codes
The most reliable way to choose the right part is to rely on the markings on the body of the old relay. However, manufacturers use different coding systems, and understanding them can be difficult. The case usually indicates the model number, electrical characteristics and compatible series of compressors.
For example, for popular brands Danfoss i Secop the marking often contains an alphanumeric code, where the last digits may indicate the type of refrigerant or voltage. Relays Indesit or Ariston are often marked with type R600 or R134a, which directly indicates the type of freon with which the system works. It is also important to pay attention to the number of contact pins - there can be three, four or even more if additional protection is present.
Often on the case you can find current characteristics designations, for example 1/4 HP or 1/3 HP. This is the engine power for which the relay is designed. If you install a part designed for less power, it will quickly fail. If it is much larger, the contacts may simply not close due to the weak current in the coil.
What do the strange symbols on the relay body mean?
Designations like 33H, 45N, 124, 145 are often found. These are compatibility codes with specific series of compressors. For example, code 33H often corresponds to Danfoss compressors of the NL series, and 45H - to the N series. It is better to look for the exact decoding in the cross-tables of spare parts suppliers.
If the marking is erased or unreadable, you will have to select an analogue based on the appearance and parameters of the compressor, which requires deeper knowledge or consultation with the seller.
Table compatibility and main brands
To simplify the search, we provide a table of correspondence between popular relay models and refrigerator brands. This will help narrow down your search if the original part is not available.
| Refrigerator brand | Typical relay manufacturer | Marking features | Common model codes |
|---|---|---|---|
| Indesit, Ariston | Indesit, Danfoss | Often PTC, mount for 2 or 3 pins | 33N, 45N, 124, 145 |
| Atlant (Atlant) | Atlant, Danfoss | Induction and PTC, specific connector | PTC-K, RTP-0 |
| Beko, Candy | Danfoss, Secop | Compact PTC relays | 124, 145, 165 |
| Liebherr, Bosch | Danfoss, Secop | High reliability, often with protection | 100N, 120N |
| Samsung, LG | Samsung, LG (OEM) | Often assembled with thermal protection | S-MRC, 4RM series |
When choosing an analogue from a third-party manufacturer (for example, Secop instead Danfoss) make sure that the fit dimensions and contact locations completely match. Even a millimeter misalignment may prevent the relay from being placed on the compressor or cause a short circuit.
Please note that some relays are sold complete with thermal protection, and some without it. If in your refrigerator the protection is separate or built into the compressor housing, there is no need to buy a relay with an additional “pill” of protection, unless the design provides for its installation in the same casing.
Diagnostics: is the relay really to blame?
Before buying a new part, you should make sure that it is the problem and not the compressor. There may be several symptoms: the refrigerator does not turn on, a hum and a click is heard, or the motor starts for a couple of seconds and stalls.
The easiest way to check is a visual inspection and a “rattle”. Remove the relay from the compressor (after disconnecting the refrigerator from the mains!). Shake it near your ear. If a ringing or knocking sound of the ceramic element is heard inside, it means that the posistor is destroyed - this is a guaranteed sign of a PTC relay malfunction. Induction relays can also make a sound when shaken, but it is duller, from the core.
Also inspect the inside of the relay. If the contacts are blackened, melted, or traces of burning and soot are visible on the walls of the housing, the part requires replacement. Sometimes it is enough to simply clean the contacts with fine sandpaper, but in the case of PTC elements, cleaning will not help - only replacement.
☑️ Diagnostics before purchase
If externally the relay looks perfect and the compressor hums and does not start, you can try to carefully close the contacts of the starting winding (only for experienced ones!). If the motor starts working, the problem is in the relay. If not, the compressor itself may be jammed or the winding is faulty.
Replacement instructions and safety precautions
Replacing the start relay is a simple procedure, but requires strict adherence to safety precautions. The work is carried out with electrical voltage and refrigerant, so caution will not hurt.
First, completely turn off the power to the refrigerator. Remove the back panel covering the compressor area. It is usually secured with latches or several screws. Allow the compressor to cool down if it has just been running. Carefully remove the old relay by pulling it down or to the side (depending on the model), after disconnecting the wires if they are not built into a common block.
Install the new relay in a strictly vertical position (usually the arrow UP or TOP should look up). This is critical for induction models where gravity is involved in opening contacts. Place the wires on the appropriate terminals. It is difficult to confuse them, since they often have different colors or markings, but it is better to check the diagram on the case or photograph.
⚠️ Attention: Never turn on the refrigerator with the back panel open and the compressor contacts exposed. This is life-threatening and may result in electric shock. Carry out all power-on checks only after installing the protective casing.
After installation, turn on the refrigerator. If you hear the engine start confidently and after a while the chamber begins to get colder, the repair has been completed successfully. If the clicks repeat, immediately turn off the device and check the connections.
Frequent errors during selection and installation
Even experienced craftsmen sometimes make mistakes, let alone beginners. One of the most common mistakes is ignoring the type of refrigerant. Relays for R134a and R600a may differ in current characteristics, since compressors for different freons have different power and starting current.
Another mistake is an attempt to “waste” the seat. If the relay does not fit, there is no need to use force or file down the plastic. Most likely, you chose the wrong model. Mechanical stress can damage the compressor contacts or the relay itself, which will lead to poor contact and sparking.
Also, you should not use “temporary” solutions, for example, short-circuiting the relay with wire so that the refrigerator can be completed before the technician arrives. This is guaranteed to lead to burnout of the engine starting winding, and then repairs will cost several times more, requiring replacement of the compressor.
Remember that if after replacing the relay the problem does not disappear, the reason may lie deeper: in the interturn short circuit of the windings or mechanical jamming of the piston group. In such cases, you cannot do without professional diagnostics.
Is it possible to use a universal relay for any refrigerator?
Universal relays exist, but they are not suitable for all models. They usually have a set of adapters or adjustable contacts. However, their reliability is often lower than that of original parts, and their service life may be limited. They should be used only as a last resort if the original cannot be found.
Why does a new relay burn out after a week?
This may indicate problems with the compressor itself (turn-to-turn short circuit, increased current consumption) or poor contact in the electrical circuit. Also, the reason may be the incorrect selection of relay by current or type (PTC instead of induction).
Where to find the marking if there is none on the relay itself?
If the marking on the relay has worn off, look for it on the sticker of the compressor (motor). It lists the type of refrigerant, the capacity, and sometimes the recommended type of starter. You can also find the compressor model and check it in the spare parts catalogues.
How much does the starting relay cost?
The price varies from 300 to 1500 rubles depending on the brand and type. Original parts for expensive brands (Liebherr, Bosch) will cost more than universal analogues for budget models (Indesit, Atlant).