The situation when refrigerator compressor makes a characteristic click, starts for a couple of seconds and immediately stalls, is one of the most alarming signals for the owner of household appliances. This mode of operation, often called "cyclic starting", indicates that the motor protection system is forcibly breaking the power circuit, preventing more serious damage or fire to the windings. Ignoring this symptom can lead to complete failure of the unit, which will require an expensive replacement of the entire unit.
There can be several reasons for this behavior: from a banal power surge in the network to a complex freon leak or mechanical jamming of the piston group. Start relay, which is responsible for starting the engine, also often becomes the culprit of the problem, since its contacts oxidize or burn over time. Understanding the physics of the process helps not only to diagnose a malfunction, but also to assess the risks of further use of the device.
In this article we will analyze in detail the mechanics of the operation of protective mechanisms and the main components, the failure of which leads to an instant shutdown of the motor. You don't have to be an engineer to understand what's going on, but basic knowledge will help you avoid mistakes during initial diagnostics. Safety is the first thing you should think about before touching the electrical components of the refrigerator.
The mechanism of operation of the thermal protection and start relay
To understand why the motor runs jerkily, you need to consider the device that starts it. In classic circuits with an asynchronous motor, starting relayis used, which supplies current to the starting winding only at the moment of switching on. As soon as the rotor reaches the required speed, the relay should open the circuit of the starting winding, leaving only the main winding to work. If this mechanism jams or the contacts stick, the engine cannot reach operating mode.
Works in parallel with the relay thermal protection relay (thermal relay). This device monitors the temperature of the compressor housing and the current flowing through it. If there is excessive heating or a surge in current, the bimetallic plate inside the relay bends and opens the contacts, de-energizing the unit. After cooling, the plate returns to its original position and the cycle repeats. It is this process that you hear as the switch-on click and subsequent silence.
⚠️ Attention: Frequent on and off cycles lead to rapid overheating of the motor windings. If you notice such a problem, operating the refrigerator in normal mode can completely “kill” the compressor in a matter of hours.
In modern inverter models, the operating principle is different, there is no classic relay with clicks, but the “instant stop” problem also occurs. In such cases inverter control unit records an error and stops supplying power to protect expensive electronics. Diagnostics of such systems requires special equipment and knowledge in the field of electronics.
What is the danger of a “cold start”?
An attempt to start the compressor immediately after it stops without waiting (at least 5-10 minutes) can lead to water hammer in the system, since the refrigerant does not have time to dissolve in the oil, which physically destroys the valves.
Malfunctions of the starting relay
The most common and easily remediable reason for the compressor turns on and offis the failure of the starting relay. This small plastic block, attached to the side or bottom of the motor, is subject to wear and tear. Inside it there is a coil and a moving core, which over time can become contaminated with insulation decay products or simply wear out mechanically.
If the relay contacts are burnt, they may not open in time, which is why the starting winding continues to receive current, which causes a sharp increase in current strength and tripping of the protection. In other cases, the relay simply cannot close the circuit to start, and the engine only hums until the thermal protection turns it off. Replacing this element is a procedure that can be done with your own hands if you have basic skills.
When diagnosing, you should pay attention to the condition of the contacts. If black deposits or melted plastic are visible on them, the element requires replacement. It is also important to check whether the installed relay matches the markings of your compressor. Installing a relay with the wrong parameters is a common mistake that will not solve the problem.
- 🔌 Visual inspection: Remove the relay and shake it. If a ringing sound is heard inside (as from broken glass), it means that the internal mechanism is damaged and requires replacement.
- 🧹 Cleaning the contacts: In some cases, carefully cleaning the contacts with fine sandpaper helps, but this is a temporary measure.
- ⚡ Checking the coil: The coil resistance must correspond to the passport data, otherwise the magnetic field will be insufficient to start.
Problems with the electrical part of the compressor
If everything is in order with the relay, the problem may lie in the engine itself. An interturn short circuit in windings is a serious fault in which the insulation between the turns of copper wire is broken. This leads to a sharp increase in current consumption, to which the thermal relay instantly reacts, breaking the circuit. In this case, the compressor may hum more than usual before turning off.
Another reason is a break in the internal wiring or failure of the thermal relay built into the motor housing. If the thermal relay “lies” and shows a critical temperature on a cold engine, it will constantly turn off the power. You can check the integrity of the windings using a multimeter by measuring the resistance between the contacts and the housing.
It is important to understand the difference between a working and a faulty motor. A working motor has a certain winding resistance, which can be found in the technical documentation. If the device shows “zero” (short circuit) or “infinity” (break), then the compressor requires replacement. Self-rewinding of motors in domestic conditions is not done due to complexity and low profitability. compressor requires replacement. Self-rewinding of motors is not done at home due to complexity and low profitability.
| Type of fault | Symptoms | Diagnostic method | Solution |
|---|---|---|---|
| Interturn short circuit | Humming, high current, protection operation | Measuring winding resistance | Replacing the compressor |
| Thermal relay malfunction | Cold shutdown, clicking | Checking the relay contacts | Replacing the thermal relay |
| Break winding | No buzz, no start | Resistance measurement (infinity) | Replacement compressor |
| Breakdown to the housing | Tripping of an RCD or knocking out plugs | Measuring the resistance between the contact and the housing | Replacing the compressor |
Mechanical wedge and problems with oil
One of the most difficult causes to eliminate is mechanical jamming of the piston group. This happens when the rubbing parts of the engine are deprived of lubrication or when water hammer occurs in the system. As a result, the piston or shaft gets stuck in a certain position, and the engine is physically unable to make the first revolution. When you try to start, a powerful buzzing sound is heard, followed by a shutdown click.
Often a “wedge” occurs after a long period of inactivity of the equipment. The oil flows into the lower part of the crankcase, thickens or becomes coked. In such cases, the “wedging” method by applying increased voltage sometimes helps, but this is a risky procedure that is best left to professionals. If the compressor is tightly jammed, no folk methods like tapping with a hammer will help.
Lack of oil in the system also leads to rapid overheating and metal scuffing. Wear products are carried throughout the system, clogging the capillary tube and filter drier. Therefore, if diagnostics show a mechanical malfunction of the motor, it is often necessary not only to replace the compressor, but also to completely flush the refrigerator circuit.
⚠️ Attention: An attempt to start a jammed compressor directly, bypassing the protective relays, is almost guaranteed to burn out the windings. Do not use this method without professional equipment.
The influence of refrigerant and freon leaks
It would seem, what does gas have to do with it if the motor is electric? However freon in modern refrigerators performs not only a cooling function, but also a cooling function for the compressor itself. The refrigerant vapor returning to the motor cools its windings. If there is a leak in the system and there is little or no freon, the engine overheats faster than usual and the thermal protection turns it off.
In addition, if there is no pressure in the system (vacuum), the compressor is easier to spin, but the lack of cooling by refrigerant vapor is a critical factor. Some models are equipped with pressure sensors that block the start of the compressor if the pressure in the circuit is below normal, preventing dry operation.
Signs of a leak are often visible to the naked eye: swelling of the back wall, oily spots under the refrigerator or on the condenser tubes. If you notice that the refrigerator has stopped freezing and the motor is running jerkily, the likelihood of a freon leak is very high. In this case, a simple reboot will not help - searching for leaks, soldering and refilling is required.
☑️ Leak diagnostics
Power surges and wiring problems
Unstable voltage in the electrical network is the scourge of modern household appliances. If the voltage drops below the permissible level (for example, below 190-200 Volts), the engine torque is not enough to start. The compressor tries to start, the current increases, but rotation does not occur, and the thermal relay turns off the unit. This situation often repeats during peak network load hours.
It is also worth checking the condition of the outlet and power cord. Oxidized contacts in a socket or plug create additional resistance, causing a voltage drop at the entrance to the refrigerator. As a result, the engine is “under-fuelled” and cannot start. Poor contact also causes sparking and heating, which is a fire hazard.
To protect equipment in unstable network conditions, it is recommended to use a voltage stabilizer or voltage control relay. These devices cut off power when the network parameters go beyond acceptable limits, protecting the electronics and motor of the refrigerator from damage.
- 📉 Low voltage: The motor hums, but does not start, the protection works after 3-5 seconds.
- 🔥 Poor contact: Heating of the plug or socket, burning smell of plastic, periodic shutdowns.
- ⚡ Pulse interference: Short-term surges can interfere with the operation of electronic modules control.
Algorithm of actions and when to call a specialist
If you are faced with the problem described, do not panic. First, unplug the refrigerator and let it stand for at least 2-3 hours. This is necessary to cool the thermal relay and equalize the pressure in the system. After turning on, listen: if the motor starts and runs normally, perhaps the problem was overheating or a power surge.
If the situation repeats, you can carefully remove the starting relay and inspect it. If you see obvious signs of burning or hear rattling, purchasing a new relay can be considered the first step towards repair. However, if you do not have experience working with electrical appliances, it is better not to climb inside the housing.
Calling a specialist is necessary if: replacing the relay did not help, there is a suspicion of a freon leak, or you hear strange metallic knocks inside the motor. Repairing a compressor unit requires evacuation of the system, charging refrigerant and using special tools, which cannot be done in the kitchen.
Is it possible to drive with a faulty compressor?
Transporting a refrigerator with a faulty but working compressor is possible, but not advisable. It is better to turn it off and carry it in a vertical position so that oil does not get into the circuit.
Why does the compressor hum, but does not start?
The hum means that current is supplied to the windings, and a magnetic field is created, but the rotor cannot turn. This is a sign of a mechanical wedge, jamming of the piston group or critically low voltage in the network. Also, the reason may be a malfunction of the starting winding or a relay that does not switch engine operating modes.
How much does it cost to replace a compressor?
The cost consists of the price of the unit itself (from 3,000 to 10,000+ rubles, depending on the model) and the work of a technician (usually from 4,000 to 8,000 rubles). You may also need to replace the filter drier and refill with freon. The total amount often makes up a significant part of the cost of a new refrigerator.
Is it possible to repair an old compressor?
In a factory environment - yes, but in household workshops, repairs of compressors (rewinding, replacing valves) are practically not carried out due to the high labor intensity and the need for hermetic welding. Usually, the unit is completely replaced with a new or refurbished analogue.
How to extend the life of a compressor?
Do not place the refrigerator close to the wall (a gap for ventilation is needed), defrost it regularly (if there is no No Frost), do not load hot foods into the chamber and keep the condenser at the back clean. It is also important to ensure stable voltage in the network.