The situation when refrigerator compressor starts with a characteristic hum, and after a few seconds a click is heard and the unit goes silent again, is critical for the safety of products. This symptom, known as a "short cycle", indicates that the protection system is activated almost instantly, preventing the engine from reaching the required speed. If no action is taken, such work can lead to complete combustion of the electric motor windings.
The reasons for this behavior lie either in the electrical part (starting relay, wiring) or in the mechanical part (jamming of the piston group, lack of refrigerant). The owner needs to listen carefully to the sounds: a quiet hum is replaced by a loud click, or only a single knock is heard without attempts to start. Understanding these nuances will help to more accurately determine the malfunction before the technician arrives.
It is important not to ignore the first signs of unstable operation, since cyclic switching on creates a colossal load on the electrical network and the unit itself. In some cases, the problem is solved by simply replacing an inexpensive component, in others, serious repairs are required and the compressor is replaced. Let's look at the main failure scenarios.
Malfunctions of the starting and thermal relay
The most common reason the compressor clicks and turns offis the failure of the start-protective relay. This small black or white box, attached to the side of the motor, is responsible for supplying the starting impulse and protecting against overheating. Inside it is a coil or posistor, which degrade over time and cease to perform its functions.
When the relay breaks, it cannot keep the contacts closed long enough to accelerate the motor rotor. As a result, the motor tries to start, the current increases sharply, and the thermal protection forcibly breaks the circuit. You hear a click and the refrigerator freezes until the next thermocouple cool cycle. Sometimes you can hear a rattling sound inside the relay if the core has collapsed.
Replacing this element often does not require calling a technician if you have electrical skills. However, it is important to select a relay with exactly the same characteristics as the burnt one, otherwise the protection system will not respond correctly to overloads. An incorrectly selected relay can lead to a fire or permanent engine failure.
⚠️ Attention: Before removing the relay, be sure to disconnect the refrigerator from the power supply! Residual voltage may remain on the contacts, and careless handling of live wiring is dangerous.
How to check a relay with a multimeter?
To check, remove the relay and shake it: if you hear a ringing sound, it means the core is broken. Test the contacts with a multimeter in resistance mode: there should be a circuit, but when heated (for thermal relays) it opens.
Interturn short circuit of the compressor windings
A more serious problem that causes the “on and off” symptom lies in the very heart of the refrigerator - the electric motor. Interturn short circuit occurs when the insulation of the windings is compromised due to overheating or aging. At this moment, the winding resistance drops, the current increases to critical values, and the thermal relay instantly cuts off the power.
It is difficult to diagnose this malfunction at home, but you can pay attention to indirect signs. Often when you try to start the refrigerator there is a smell of burning or scorched insulation coming from the back of the refrigerator. The compressor housing can heat up to very high temperatures in a matter of seconds of operation.
If the winding is burned out, repair is usually impractical, since rewinding the motor at home is impossible, and the cost of a new compressor with operation is high. For owners of old models Atlant or Biryusa sometimes it is easier to buy a new refrigerator than to change the “motor”.
- 🔥 Pungent burning smell when trying to start.
- ⚡ Knocks out automatic plugs or RCDs in the panel.
- 🌡️ The compressor housing heats up in 10-15 seconds.
- 🔇 Complete absence of buzzing, only a quiet click.
Mechanical jamming of the piston group
Sometimes the electrical part is working, but the engine rotor is physically unable to turn. This state is called compressor wedge. It occurs when the service life of rubbing parts is exhausted, metal shavings get into the cylinder, or the oil thickens in severe frost. The motor tries to make a jerk, a strained hum is heard, but the shaft stands still.
The protective relay in this case works normally: it sees that the current consumption has increased (the engine does not spin, but the current flows), and opens the circuit. The characteristic sound of a wedge is a low-frequency hum that turns into a click. If you leave the refrigerator in this condition, the windings will burn out very quickly.
There is a method of “treating” the wedge by increasing the voltage or using a special capacitor, but this is a temporary measure that will only delay the final breakdown. Mechanical destruction of components inside the HDA is irreversible. In some cases, changing the oil and flushing the system helps, but this is expensive and time-consuming.
Problems with the piezorelay (in inverter models)
In modern refrigerators with a system No Frost and inverter control, there may not be a traditional starting relay. Its function is performed by an electronic module or piezoelectric relay. If an inverter compressor turns on and then turns off immediately, the reason often lies in an electronics failure or a malfunction of the piezo element itself.
The electronics may not produce the required frequency to start, or the temperature sensors may transmit incorrect data to the control board. Unlike conventional relays, diagnostics here require special equipment. You can independently only check the integrity of the wiring going to the compressor.
A frequent problem in inverter models LG or Samsung is the oxidation of the contacts in the connector between the board and the compressor. Vibration during operation gradually weakens the connection, resulting in signal loss and emergency stop. Checking and cleaning the contacts sometimes brings the unit back to life.
Lack or absence of refrigerant
It would seem, what does freon have to do with it if there is a problem with starting? However refrigerant leak directly affects the operation of the compressor. In some refrigerator models, especially older ones, the pressure in the system indirectly affects the load. But another situation is more common: the compressor works normally, but due to the lack of freon it does not cool, and the thermostat quickly turns it off, creating the illusion of a motor breakdown.
However, if the compressor just “starts and stops” (turns on for 2-3 seconds and clicks), this may indicate that the protection system reacts to overheating due to the lack of cooling of the windings with freon (in some designs) or to “idling” operation at low pressure, which is also an emergency mode.
You can determine a leak by a swollen back wall inside the freezer or by the lack of cooling when the motor is running (albeit for a short time). If the tubes are hot and the chamber is warm, most likely the freon has come out.
| Symptom | Probable cause | Difficulty of repair | Required tools |
|---|---|---|---|
| Click after 1-3 seconds | Start relay | Low | Screwdriver, multimeter |
| Hum and click | Compressor wedge | High (replacement) | Replacement kit, burner |
| Smell of burning | Winding burned out | High (replacement) | Replacement kit, burner |
| Works, but does not freeze | Freon leak | Average | Vacuumator, freon, scales |
Low voltage in the network and oxidation of contacts
Do not discount external factors. If your apartment low voltage is online (less than 190-200 Volts), the compressor may simply not have the strength to start. The motor hums, trying to turn over, the current increases, and the thermal protection turns it off. This often happens in holiday villages or during peak network load hours.
The problem may also lie in the socket or extension cord. Oxidized contacts, loose connections or too thin extension cord create a voltage drop precisely at the moment of start-up, when current consumption is maximum. As a result, insufficient power reaches the compressor.
Check the operation of the refrigerator by plugging it directly into another outlet, preferably without extension cords and surge protectors. If the problem disappears, the cause was a bad connection or cable. The use of powerful voltage stabilizers can save equipment in unstable network conditions.
⚠️ Attention: Do not use cheap Chinese extension cords with thin wires to connect refrigerators. At the moment of startup, they create a critical voltage drop, which kills the compressor.
☑️ Diagnostics before calling a technician
Frequently asked questions (FAQ)
Is it possible to operate the refrigerator if it turns on and off?
It is absolutely not possible. Prolonged operation in the "start-stop" mode will lead to overheating and final combustion of the compressor windings, which will make repairs economically impractical. Disconnect the device from the network.
How much does it cost to replace the starting relay?
The relay itself is inexpensive (from 300 to 1500 rubles depending on the model), but if you do not know how to change it yourself, you will have to pay for the work of a specialist. In service, this service usually costs 1500-3000 rubles including a spare part.
Why does the compressor hum but does not start?
This is a classic sign of a mechanical wedge of the piston group or an interturn short circuit. The motor does not have enough power to turn over, or it is physically jammed. Diagnostics by a technician is required.
Is it possible to start a compressor without a relay?
Theoretically, you can start it by applying voltage directly to the starting winding, but it will not work for long and is dangerous without protection. Operating a refrigerator without a start-up protection relay is prohibited by safety rules.
What to do if, after defrosting, the refrigerator stops starting normally?
Moisture may have gotten into the electrical contacts or on the relay. Let the refrigerator stand turned off for 12-24 hours in a dry room. If the problem does not go away, drying and replacement of components will be required.