When the refrigerator suddenly stops freezing, and the compressor only hums for a few seconds and clicks, trying to start, or is silent, the first thing an experienced technician looks at is the start-up protection device. It is this small element that is responsible for starting the engine and protecting it from overloads. Understanding what it looks like starting relayis necessary for every owner of household appliances who wants to carry out an initial diagnosis of a fault without calling a specialist.
Externally, it is a compact part, hidden from the user’s eyes in the lower part of the unit, behind a plastic cover or directly on the motor housing. Its dimensions usually do not exceed the dimensions of a matchbox, and its weight is only a few tens of grams. Despite its small size, it is the performance of this unit that determines whether compressor the refrigerant will start and begin to circulate through the system.
It is better to start a visual acquaintance with the relay by studying its location, since the appearance may vary depending on the manufacturer of the refrigerator. Old Soviet-made models and modern units use different types of devices, but their functional purpose remains unchanged. If you plan to do the inspection yourself, it's important to know what to look for and what parts to pay attention to first.
Location and access to the starter
To see what the starter relay looks like, you need to gain access to the bottom of the refrigerator. In most modern models, the compressor unit is located in a niche on the rear wall, covered with a metal or plastic casing. Removing this cover reveals a black spherical or cylindrical compressorto which the required part is attached.
The relay is always put directly on the side output of the electric motor shaft. It can be covered with an additional plastic casing to protect it from dust and moisture, but most often it is open. Fastening is carried out due to a tight fit on the fittings and fixation with a spring bracket or plastic latches. When dismantling, it is important not to damage the associated wires, which can become fragile over time.
⚠️ Warning: Before removing the protective cover and touching any electrical components, be sure to unplug the refrigerator. Residual voltage or accidental shorting of contacts can lead to electric shock.
After removing the fixing bracket or loosening the clamps, the device can be easily removed by hand. It is held on by three contact pins extending from the compressor housing. It is at this moment that the very element that needs to be identified appears before you. Its position is strictly vertical or with a slight inclination, which is determined by the design of the trigger mechanism.
Design features and appearance
Visually, the starting relay is a box made of heat-resistant plastic or bakelite. The body color is most often black, white or gray, depending on the manufacturer. On the front side there is usually a marking with technical characteristics, part number and connection diagram. This data is critically important when selecting analogue a replacement.
Inside the case there is a complex system of contacts, springs and moving elements. Depending on the type of device, the internal contents may vary. There are induction (electromagnetic) and posistor relays. The former have a movable core with a contact group, the latter have a ceramic element (posistor) that changes its resistance when heated. You can determine the type if you carefully open the case, although modern parts are often made non-separable.
Three main contacts go to the bottom of the case, which are put on the compressor terminals. They are located in a strictly defined order: one general and two starting (or working and starting). The shape of the contacts can be round or rectangular, and their material is brass with silver plating for better conductivity. Oxidation of these contacts is a common cause of unstable operation.
What is inside a non-separable relay?
Inside the plastic case there is a spring mechanism with a moving contact and a coil. When current is applied, the coil creates a magnetic field, which draws in the core and closes the contacts, starting the engine.
Particular attention should be paid to the condition of the housing. If traces of melting, soot, or a characteristic burning smell are visible on the plastic, this indicates overheating and breakdown. In such cases, the insides of the device often turn into a sintered mass that cannot be restored. A serviceable relay must have a clean, damage-free body and tight-fitting terminals.
Types of starting devices
Understanding what a starting relay looks like is impossible without analyzing its main types. In household appliances, there are most often two types of devices, the principles of which differ significantly. Knowing these differences helps to more accurately diagnose a malfunction and select the correct replacement.
The first type is induction (electromagnetic) relay. It looks more massive and heavy. Inside there is a coil through which the motor winding current passes. When starting, the current is high, the magnetic field draws in the core, short-circuiting the starting winding. When the engine picks up speed, the current drops, the core under the influence of gravity (that's why position is important!) falls and opens the circuit. Such relays are often marked PTC in the name, although this is not entirely correct, but there are also purely electromagnetic options.
The second type is positor (thermal) relay. It is lighter and more compact. A posistor is installed inside - a ceramic element that at room temperature has low resistance and passes current to the starting winding. The passing current heats up the posistor, its resistance increases sharply, and the current practically stops flowing, opening the circuit. Such devices are less sensitive to position, but are afraid of shock.
- 🔌 Induction relays - sensitive to orientation in space, require strictly vertical installation, often used in older models and powerful compressors.
- 🔥 Posistor relays - do not have moving mechanical parts (except for thermal protection contacts), are more reliable, but require time to cool down (3-5 minutes) before restarting.
- ⚙️ Combined devices - combine the functions of starting and thermal protection, look like a single unit, put on three pins of the compressor.
Visual signs of a malfunction
Relay diagnostics often begin with a visual inspection. Even without testing with a multimeter, you can identify a number of characteristic defects. If you take out the device and see that it looks different than in the photo of working analogues, this is a cause for alarm.
The first sign is the presence of holes or burns on the case. If a spark breaks through the plastic, black dots or through holes remain on the surface. This means that an arc discharge occurred inside, and the contacts could be welded or, conversely, destroyed. Operating such a relay is strictly prohibitedas this can lead to combustion of the compressor windings.
The second sign is rattling inside the housing when shaken. In a working induction relay, the core is fixed, but in a posistor relay, the elements are filled with compound or sit tightly in the sockets. If you hear knocking noise from ceramic elements or metal parts, it means that the internal structure is damaged. The posistor could have cracked due to thermal shock, which makes it unusable.
⚠️ Attention: If, upon external inspection, traces of oxidation are visible on the contacts (green or black coating), this does not always mean a breakdown of the relay itself. Sometimes it is enough to clean the contacts, but if the oxidation is deep, it is better to replace the entire assembly.
The third sign is the smell. A working device does not smell anything. If the isulator emits a strong smell of burning plastic or burning, this is a sure sign of overheating. Often such changes are visible in the color of the body - it may become yellowish or brownish in areas of heating. Thermal deformation of the plastic also indicates that the device was operating in emergency mode.
Comparative table of characteristics
For ease of identification and selection of spare parts, it is convenient to use comparative data. Different models of refrigerators require the installation of relays with certain parameters. Below is a table to help you understand the main differences.
| Parameter | Induction relay | Posistor relay | Thermal protection relay |
|---|---|---|---|
| Principle actions | Electromagnetic field | Change in resistance when heated | Opening of the bimetallic plate |
| Sensitivity to position | High (only vertically) | Low (works in any position) | Depends on the design |
| Restart time | Instantly (after the contacts have cooled) | 3-5 minutes (cooling posistor) | Depends on the cooling time of the plate |
| Typical resource | High, but there is mechanical wear | Limited by the number of heating cycles | High |
When choosing a replacement, it is important to pay attention not only to the appearance, but also to the rated current. It is indicated on the labeling (for example, 1/4 HP, 1/3 HP or in Amperes). Installing a relay with an inappropriate response current will result in the compressor either not starting or overloading, which will reduce the life of the motor motor.
☑️ Check before purchasing a new relay
Removal process and installation
Replacing the start relay is a procedure that is accessible even to a beginner, if you act carefully. After disconnecting the refrigerator from the network and removing the back cover, you need to disconnect the wires going to the relay. They can be fixed with latches or simply sit tightly on the contacts.
Removing the relay itself from the compressor shaft requires caution. Do not pull the wires or apply excessive force to avoid breaking the ceramic motor lead tubes. The relay needs to be loosened with light movements from side to side, while simultaneously pulling it up. Often it is removed together with the thermal protection, representing a single block.
Installation of a new part is done in the reverse order. It is important to ensure that the relay is pushed in all the way and the contacts fit snugly to the compressor terminals. If a spring clip is used, it must be replaced. After assembly, do not rush to close the casing - turn on the refrigerator and listen. Start-up should be soft, without strong clicks or buzzing.
⚠️ Attention: Technical characteristics of compressors and requirements for starting devices may differ from one manufacturer to another. Always check the markings on the new relay with the data on the nameplate of your refrigerator or the old part.
If after replacing the relay the refrigerator worked normally, then the problem was in this particular unit. However, if the situation repeats itself after a short time, perhaps the reason lies deeper - in the compressor itself or the power supply system. In such cases, a more in-depth diagnostics using professional equipment is required.
Frequently asked questions (FAQ)
Is it possible to repair a burnt-out starting relay yourself?
Theoretically, you can try to restore dismountable induction relays: clean the contacts with sandpaper, wash with alcohol and reassemble. However, posistor relays cannot be repaired. Considering the low cost of a new part, repairing an old one is often impractical and less reliable.
Why does the relay heat up during operation?
A slight heating of the housing up to 40-50 degrees may be the norm, especially for thermal protection relays. However, if the case is so hot that it is impossible to touch it, or a burning smell is felt, this is a sign of faulty contacts, sticking of the core, or incorrect selection of the device according to the current.
How often do you need to change the starting relay?
The service life of a high-quality relay is designed for thousands of switching cycles and can be 10 years or more. No scheduled replacement required. They change the part only when signs of a malfunction appear: the refrigerator stops turning on, clicks are heard, but there is no start, or the thermal protection is triggered.
Does dust affect the operation of the relay?
Yes, a thick layer of conductive dust or metal shavings can cause a short circuit between the contacts. That is why it is important to keep the lower part of the refrigerator, where the compressor is located, clean and periodically remove dust with a vacuum cleaner.
Is it possible to start a refrigerator without a relay?
Technically, you can start a three-phase or two-winding compressor motor without a starting device using an external starting circuit, but this is a temporary measure. Long-term operation without a standard relay will lead to overheating and burnout of the starting winding.