A sudden stop of the compressor is always stressful for the owner of household appliances, because the safety of products depends on this unit. Often the cause of failure is not the motor itself, but its starting relay, which is responsible for starting the motor and protecting the windings from overloads. If the refrigerator hums, clicks, but does not start, or the compressor only works for a few seconds before turning off, there is a high probability that the problem lies in this small but critical element of the electrical circuit.
Before calling a technician or buying new equipment, it makes sense to conduct an initial diagnosis. Start-protection relay is a device that is physically connected to the contacts of the compressor and often fails due to power surges or natural wear of the contacts. In this article, we will look in detail at how to determine the malfunction, what tools will be needed for checking, and whether it is possible to restore the operation of the refrigerator on your own without deep knowledge in electrical engineering.
It is important to understand that ignoring the symptoms of a faulty relay can lead to more serious consequences, including burning windings compressor. Therefore, if you notice uncharacteristic behavior of your unit, do not delay the inspection. Correct and timely diagnostics will help save a significant amount on repairs and extend the life of your refrigerator.
Signs of a faulty start relay
The first step in diagnosis is always observing the behavior of the equipment. Symptoms may may vary, but they almost always indicate problems in the engine starting circuit. If the relay is stuck in the closed state, the compressor will work continuously, which will lead to severe overcooling of the chambers and icing of the evaporator.
In the opposite situation, when the contacts do not close, you will hear a characteristic click, followed by silence or the hum of a motor that cannot start. Thermal protection in this case, it will work after a few seconds, turning off the power to prevent overheating.
- 🔊 The compressor makes a loud click, hums for 3-5 seconds and turns off - this is a classic sign that starting winding does not receive an impulse to start.
- ❄️ The refrigerator compartment does not cool, although the light inside is on and the fan (if any) is working - this means that the refrigerant does not circulate due to the motor stopping.
- 🔥 The relay housing or itself the compressor gets very hot even after a short operating cycle - this is a signal of an overload or short circuit inside the part.
Sometimes users notice that the refrigerator begins to work unstably: it freezes perfectly, then it stops. This may indicate floating defectthe contacts inside the relay are burning or oxidizing, creating an unstable connection. In such cases, a visual inspection may not yield anything, and an instrumental check will be required.
Design and principle of operation relay
To effectively test a part, you need to understand how it works. In modern refrigerators, most often there are electromagnetic (starting) and thermal (protective) relays, often combined into one housing. An electromagnetic relay operates on the principle of 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 motor rotor picks up speed, the current in the circuit drops, the magnetic field weakens, and the core is affected gravity or spring returns to its original position, opening the starting circuit. Thermal relay works differently: it contains a bimetallic plate that bends when heated by a passing current. If the current exceeds the norm (overload) or the compressor is too hot, the contacts open, stopping the engine.
There may also be a capacitor inside the housing, which helps smooth out the starting currents and make it easier to start the engine. In older models, relays with a posistor could be used, but in classical circuits it is the one that dominates. Understanding this mechanics is important, since the malfunction can lie not only in the electrical circuit, but also in the mechanical sticking of the core. induction coil. Understanding this mechanics is important, since the fault may lie not only in the electrical circuit, but also in the mechanical sticking of the core.
What is the difference between a relay for a single-phase and a two-phase motor?
In single-phase motors (most household refrigerators), a relay is needed to create a phase shift and start rotor rotation. In two-phase or three-phase industrial units, other switching circuits are used, and a conventional household relay is not applicable there.
Preparation for diagnostics: tools and safety
Before starting any work, you must strictly follow the electrical safety rules. Disconnection from the network is the first and mandatory action. Even if it seems to you that you won’t hit anything, the risk of electric shock when working with 220V mains voltage is too great.
To carry out high-quality diagnostics, you will need a minimum set of tools. The main device will be multimeter (tester), which will allow you to measure the resistance of the windings and check the integrity of the circuit. You may also need a flat-head and Phillips-head screwdriver to remove the casing, pliers and possibly fine sandpaper to clean the contacts if you plan to restore the part (although this is a temporary solution). from the mains
☑️ Preparing to test the relay
It is important to ensure good lighting of the work area, since contacts and markings on parts may be small and difficult to see in the shadows. If you are working alone, make sure the refrigerator is stable and will not tip over when removing the panels. Remember that the compressor may retain a residual charge, so do not touch the contacts with bare hands immediately after disconnecting.
⚠️ Attention: Never take measurements with a multimeter on a plugged-in refrigerator unless you are a qualified electrician. Checking the resistance is performed only on completely de-energized equipment!
Visual inspection and dismantling of the part
After removing the protective panel at the back of the refrigerator, you will see a black cylindrical or pear-shaped compressor. A plastic box fits to its side - this is what we are looking for start relay. It is usually attached to three contacts coming out of the compressor, and can be additionally secured with a bracket or spring clip.
Carefully remove the relay. In some models it is simply put on the contacts, in others you need to bend the metal bracket. Pay attention to the appearance of the part: the presence of soot, melted plastic, swelling or traces of burning clearly indicates that the part requires replacement. If a knocking sound is heard inside the case when shaken, it means that the internal mechanisms are destroyed.
The relay case is usually marked with a marking indicating the model, voltage and type of refrigerant. Also, the arrow UP or inscription This side up indicates how to correctly orient the part during installation. Position relay critically important: if you place it upside down, the gravity mechanism will not work and the compressor will not start or will burn out.
| External sign | Probable cause | Action |
|---|---|---|
| Melted body or contacts | Overheating due to poor contact or overload | Relay replacement is required |
| Rust on terminals | Moisture ingress, oxidation | Cleaning or replacement |
| Cracks in plastic | Mechanical damage, thermal expansion | Replacement (risk of short circuit) |
| Traces of soot inside | Sparking contacts, short circuit | Relay replacement and check compressor |
How to test a relay with a multimeter: step-by-step instructions
The most reliable way to check is to measure the resistance with a multimeter. Switch the device to resistance measurement mode (range 200 Ohm or continuity mode). First check the continuity between the input and output contacts. If the relay is working properly, in a certain position (usually in the working position, “feet down”) the circuit should close, and the device will show a resistance close to zero or emit a sound signal.
Then turn the relay over (imitating the position when the engine has already started and the core has dropped). In this position, the starting winding circuit should open, and the device should show infinity (1 or OL). If the resistance does not change when turned over or shows zero in both positions, the relay is faulty.
Separately, it is worth checking the thermal protection if it is built into the relay body or comes as a separate “pill”. Ring its contacts: when cold, the resistance should be zero. If the device shows an open circuit, it means bimetallic plate it has burned out or lost contact, and the circuit does not close.
- 📉 The resistance between contacts 1-3 (starting winding) should be zero at the moment of start and go to infinity after "start".
- 📈 The resistance between contacts 1-2 (working winding) is checked through the thermal protection circuit and should also be minimal.
- 🚫 If the multimeter shows infinity everywhere - the circuit is broken, if zero is everywhere (in both positions) - the contacts are stuck.
Do not forget that some modern relays with posistors behave differently: when voltage is applied, their resistance increases, opening the circuit. It is difficult to check a posistor by regular ringing, since it requires time to cool down between measurements. For such parts, the most accurate method of checking remains replacement with a known-good analogue.
⚠️ Attention: If after replacing the relay the situation repeats (the new relay burns out or the compressor does not start again), the problem may be in the compressor itself (turn-to-turn short circuit) or in low voltage in the network. It is dangerous to continue experiments.
Replacing the relay and checking the result
If diagnostics confirm a malfunction, the relay must be replaced. You need to buy a part with exactly the same markings or a complete analogue, suitable for engine power and type of refrigerant. Installation is carried out in the reverse order: carefully place the relay on the three pins of the compressor, observing the orientation (arrow UP should face up).
Secure the part with a bracket or clamp, if provided for by the design. Make sure the wires are not pinched or touching hot parts of the compressor. After assembly, do not rush to close the back panel - first perform a test run.
Plug in the refrigerator. If you did everything correctly, the compressor should start with a characteristic hum, and after a while (usually 10-20 minutes) the chambers will begin to feel cold. If the start-up was successful and the refrigerator operates stably for an hour, the repair can be considered complete.
Is it possible to repair the relay with your own hands?
Theoretically, you can clean the contacts or bend the spring, but practice shows that such a solution does not work for long. The metal of the contacts has already burned out, and in a week or two the problem will return. It is better to replace the entire part - it is inexpensive and guarantees reliability.
Frequently asked questions (FAQ)
How much does a starting relay for a refrigerator cost?
The price depends on the model of the refrigerator and the manufacturer of the relay. On average, the cost varies from 500 to 2000 rubles. Original parts for brands like Indesit or Atlant may cost more than universal analogues.
Is it possible to start a refrigerator without a relay?
You can start the compressor for a short time by applying voltage directly to the starting winding, but this is strictly not recommended without special knowledge. This may result in immediate burnout of the motor windings or personal injury. A relay is an essential element of the system.
Why does a new relay burn out immediately after installation?
This indicates a deeper problem. Most often, the compressor itself is to blame (the piston group is stuck or the winding insulation is broken), which consumes too much starting current. Also, the cause may be a malfunction of the thermostat or problems with the voltage in the network.
How often do you need to change the relay?
The service life of the starting relay is designed for the entire service life of the refrigerator (10-15 years). It is not a consumable item and is replaced only in case of breakdown. Frequent replacements indicate a malfunction of other components of the unit.