Sudden stoppage of the compressor is one of the most common reasons why the refrigerator stops cooling food. Equipment owners often panic, assuming that an expensive motor has burned out, but statistics show that in a significant number of cases the problem lies in a small but critical element of the starting circuit. This component is called start relay, and replacing it is much cheaper than repairing or replacing the compressor itself.
Understanding how this unit functions and what signs indicate it is faulty will save you time and money. Instead of calling a technician for an initial diagnosis, you can independently conduct a visual inspection and a basic check of the performance of the part. It is only important to observe safety measures and strictly follow the algorithm of actions.
In this article we will analyze the structure of the mechanism in detail, describe the symptoms of failure and provide a step-by-step testing algorithm using a multimeter. You will learn to distinguish a burnt winding from stuck contacts and understand in which cases repair is possible on your own, and when it is better to turn to professionals.
Design and operating principle of a starting relay
The starting relay is an electromagnetic switch that is responsible for starting the compressor engine. When the refrigerator is turned on, the motor rotor is stationary, and spinning it up requires significantly more current than maintaining operation. It is the relay that supplies this impulse to the starting winding, and then turns it off when the engine reaches the required speed.
There are two main types of these devices that are found in household appliances: posistor and induction. Posistor models are more modern and common in refrigerators of the latest generations, such as Indesit or Stinol. Inside them there is a ceramic element (posistor), which, when heated by current, sharply increases its resistance, breaking the starting winding circuit.
Induction, or electromagnetic relays, can often be found in older Soviet-made models or in powerful industrial units. Their operation is based on the movement of the core inside the coil: when current is applied, the core retracts and closes the contacts, and when a certain speed of rotation of the rotor is reached, the current drops and the spring opens the circuit. A critical difference is the presence of moving mechanical parts in induction models, which makes them more susceptible to wear and sticking of contacts.
Regardless of the type of design, they have the same task: to provide a short-term voltage supply to the starting winding and turn it off in time. If this process is disrupted, the compressor will either not start at all or will work with overload, which will ultimately lead to its combustion.
Why does the relay burn out?
The most common cause of failure is unstable voltage in the network or natural wear of the contacts. Frequent power surges also have a negative impact, which force the device to operate in extreme modes, overheating the internal elements.
External signs of malfunction and initial diagnostics
Before you begin disassembling the unit, you must carefully listen to the operation of the refrigerator. Characteristic sounds often tell an experienced technician exactly where the problem lies. If you hear a loud click, followed by a motor hum that lasts 3-5 seconds, and then a click that fades away, this is a classic symptom of a bad start relay or a stuck compressor.
A visual inspection can also provide a lot of information. If the compressor is hot to the touch, but the refrigerator is not freezing, this indicates that the motor is trying to start, but cannot turn the shaft. In such a situation, a protective thermal relay (which is often built into the same housing or located nearby) heats up and opens the circuit, preventing a fire.
- 🔊 Frequent clicks: Periodic turning on and off of the motor with the characteristic sound of metal hitting metal.
- 🔥 Overheating of the case: The compressor becomes excessively hot for a short operating time.
- 💡 Lack of cold: The internal chamber of the refrigerator is at ambient temperature, despite the working light.
- ⚡ Knocking out plugs: In rare cases, a short circuit inside the relay can cause the circuit breaker to operate in electrical panel.
If you observe similar symptoms, there is a high probability that the problem lies in the starting circuit. However, you should not ignore other possible reasons, such as an interturn short circuit of the windings of the engine itself or a violation of the tightness of the freon circuit.
Removal of the relay and visual inspection
To carry out an accurate diagnosis, it is necessary to remove the part from the compressor housing. Before starting any work strictly prohibited leave the refrigerator plugged in. Disconnect the power cord and move the unit away from the wall, providing access to the rear panel.
Remove the protective plastic or metal cover covering the compressor. It is usually secured with latches or several screws. Under the cover you will see a black cylindrical or pear-shaped compressor tank, the end of which has an electrical connector. This is where our desired device is located.
Carefully remove the block from the compressor contacts. In some models, it may be fixed with a metal bracket or a plastic clip that needs to be squeezed out. After removing the block, remove the relay itself from it. It is a small plastic block, often black or white, with three contacts for connecting to the compressor.
☑️ Safe dismantling
Now conduct a thorough visual inspection of the part. Shake it near your ear: if you hear ringing or knocking inside, it means that the internal elements are destroyed or torn off. This is a 100% sign that the part requires replacement. Also pay attention to the presence of traces of burning, melting of plastic or black spots on the contacts - all this indicates a breakdown or overheating.
⚠️ Attention: If cracks or traces of exposure to high temperatures are visible on the relay body, further testing with a multimeter may be impractical - the device is clearly faulty and requires replacement.
Checking with a multimeter: step-by-step instructions
The most accurate diagnostic method is to check the electrical resistance using a multimeter (tester). This device will allow you to determine the integrity of the windings and the condition of the contacts. Switch the multimeter to resistance measurement mode (Ohm) to a limit of 200 Ohm.
For posistor relays, testing is done by measuring the resistance between the contacts. In a cold state, the resistance should be within normal limits (usually several tens of Ohms), and when heated, it should go to infinity. However, it is difficult to check the dynamic change in resistance without special equipment, so the integrity of the circuit is checked more often.
Take the multimeter probes and apply them to the relay contacts. If the device shows one or an infinity sign at the measurement limit, it means there is an open circuit. If the resistance is close to zero, a short circuit is possible. Normal readings depend on the specific model, but, as a rule, range from 20 to 60 Ohms for a working posistor.
| Test type | Indications of a working relay | Indications of a faulty relay | Probable cause |
|---|---|---|---|
| Contact resistance | 20-60 Ohm (for a posistor) | 0 Ohm or ∞ (infinity) | Short circuit or open circuit |
| Visual inspection | Clean contacts, no smell | Burn, soot, melting | Overheating, insulation breakdown |
| Sound when shaking | Silence | Ringing, knocking, rattling | Destruction of the ceramic element |
| Coil integrity (for electromagnetic) | Low resistance | Infinity | Breakage of the coil winding |
If you have the opportunity, you can test under voltage, but this requires extreme caution and the presence of insulated probes. When 220V is supplied to the input contacts, voltage should appear at the output, which then disappears after 1-2 seconds (for a posistor). Remember that working with 220V voltage is deadly without the appropriate skills!
Typical errors in diagnostics and repair
Many novice technicians make mistakes that can lead to repeated breakdown or damage to the compressor. One of the most common is ignoring the condition of the motor itself. If the compressor is mechanically jammed, then even a new working relay will click and turn off, trying to start the engine, but will eventually burn out.
The wrong selection of an analogue is also common. Start relays are not universal. They are selected strictly according to the power and type of compressor. Installing a relay with unsuitable characteristics can result in the starting winding working for too long, which will cause it to overheat and burn out.
- ❌ Ignoring the thermal relay: Often a thermal relay (tablet) is paired with a starting one. When changing one, it is worth checking or replacing the second, since they work in conjunction.
- ❌ Cleaning contacts: An attempt to clean burnt contacts with sandpaper in modern posistor relays is useless, since the geometry and properties of the material are violated.
- ❌ Checking without load: Testing with a multimeter does not always reveal defects that appear only under high voltage and current.
It is important to understand that if after replacing the relay the situation has not changed, the problem may be deeper. Professional diagnostics may be required by measuring current consumption and pressure in the system.
⚠️ Attention: Never leave the refrigerator turned on with a faulty start relay for a long time. Constant attempts to start can damage the compressor windings, the repair of which is not economically feasible.
Relay replacement and final recommendations
If diagnostics confirm a malfunction, you must purchase a new component. Look for markings on the body of the old part - this may be the manufacturer's code (for example PTM-R, RAT etc.) or catalog number. Specialized household appliance stores or radio markets will help you choose an exact analogue.
The process of installing a new part is simple and the reverse of the removal process. Insert the new relay into the block, observing the position of the contacts (usually they have a certain shape and cannot fit correctly, but it is better to check the diagram or photo taken before disassembly). Place the block on the compressor contacts until you hear a characteristic click.
After assembly, turn on the refrigerator. The first minutes of operation should pass without loud clicks or buzzing. The compressor should start smoothly, with a quiet hum, and after a while begin to cool the chambers. If everything went well, install the back cover in place.
Regularly check the condition of the seals and the cleanliness of the condenser on the rear wall to reduce the load on the engine. This will extend the life of not only the compressor, but also the starting relay, ensuring stable operation of your household appliances for many years.
Frequently asked questions (FAQ)
Is it possible to start a refrigerator without a starting relay?
Theoretically, you can try to start the compressor by applying voltage directly to the starting winding for a short time, but this is extremely dangerous and requires special skills. Without a relay, the compressor will not be able to switch to operating mode and will quickly burn out. It is strictly not recommended to do this at home.
How much does a starting relay cost and is it difficult to find?
The cost of the part varies from 300 to 1500 rubles, depending on the model and manufacturer. You can find them in spare parts stores for household appliances, at radio markets, or order online according to the markings. This is a common consumable.
Why does a new relay burn out immediately after installation?
This may indicate a more serious problem: a jammed compressor, a malfunction in the electrical wiring of the refrigerator, or an incorrect selection of the relay model (not suitable for current or type). Also, the reason may be a power surge in the network.
Does the relay for Atlant refrigerators differ from other brands?
Yes, they may differ in design and parameters. For refrigerators Atlant specific relay models are often used, which are not always interchangeable with analogues from Indesit or Beko. Always check the markings.