The situation when the refrigerator turns on and turns off after a few secondsis a classic symptom of a malfunction of the starting group or the compressor motor itself. In technical documentation, this phenomenon is often called “humming” or “clicking”, since the user hears the characteristic hum of a running engine, which ends abruptly with a click. This behavior indicates that the unit is trying to start, but the protective mechanism instantly de-energizes the system to prevent overheating or short circuiting. If you ignore these signals, you can bring expensive equipment to the point of completely replacing the heart of the refrigerator.
The cyclic mode of operation, when the interval between turning on and off is only 5-15 seconds, is absolutely not the norm for modern models Indesit, Atlant or Bosch. In normal mode, the compressor should turn off only after reaching the set temperature inside the chambers, which takes from 20 minutes to an hour. Short cycles indicate that starting relay or the motor windings are under critical load. It is important to understand that each such unsuccessful start heats the windings, gradually destroying the insulation and bringing closer the moment when the motor burns out completely.
The first thing to do when such an anomaly is detected is to listen carefully to the sounds coming from the back of the unit. A loud humming sound that turns into a click most often indicates a jammed piston group or a failure of the starting device. If you hear a quiet hum that subsides without a click, the problem may lie in the electrical circuit or thermostat. It is critical to immediately disconnect the device from the power supply If there is a burning smell or visible sparking, as this can lead to a fire.
Principle of operation starting relay and compressor protection
To understand why the failure occurs, you need to understand the mechanics of starting the electric motor. The refrigerator compressor is an asynchronous motor, which requires a short-term connection of an additional starting winding to start rotating the shaft. This function is performed starting relay, which closes the starting winding circuit only at the moment of start. As soon as the rotor reaches the required speed, the relay opens the circuit and the engine continues to operate on the main winding. If this mechanism fails, the motor hums but does not rotate, which causes a sharp drop in current.
Responsible for process safety thermal protection relay, often combined with a starting relay in the same housing. It responds to the strength of the current flowing through the windings. When the rotor jams or the starting system malfunctions, the current increases significantly, heating the bimetallic plate inside the relay. The plate bends and opens the contacts, de-energizing the compressor. After some time, when the plate cools down, it closes the contacts again and the cycle repeats. It is this process that we observe as short switching on and off.
⚠️ Attention: Frequent attempts to start with a faulty relay can lead to an interturn short circuit in the compressor windings. If you hear characteristic clicks every 10-20 seconds, do not leave the refrigerator plugged in for more than 30 minutes of diagnostics.
In modern inverter models, such as Samsung with a digital inverter or LG Linear Compressor, the operating principle is different. There is no classic start relay, and the start is controlled by an electronic control module. If such a refrigerator turns on and turns off immediately, the problem most often lies in the inverter unit itself or in the loss of compression pressure, and not in the mechanical relay. Diagnostics of such systems requires special equipment and knowledge of electronics.
Diagnostics of the starting and thermal relay
The most likely reason (in 70% of cases) The refrigerator clicks and does not startis the failure of the starting relay. This is an inexpensive part, but its replacement requires accurate diagnosis. The relay can burn out due to voltage surges, natural contact wear, or moisture. Visually, there should be no cracks, melting or traces of burning on the body of a serviceable relay. If you see blackened plastic or smell burnt plastic, the part needs to be replaced.
To check the relay, it must be removed from the compressor. It is usually attached to three pins extending from the motor housing. Carefully disconnect the wires and remove the plastic casing. Inside you will find a coil with copper winding and a movable core. Check the integrity of the coil: if the winding is blackened or has breaks, the relay is faulty. Also check the mobility of the core - it should move freely inside the coil under the influence of gravity when the relay is inverted.
The thermal relay, which is often assembled with the starting relay, is checked using the “continuity” method with a multimeter. In a cold state, the contacts should be closed (resistance close to zero). If the multimeter shows infinity, then the circuit is open and no current is flowing to the motor. However, even if the ringing shows normal, the relay may falsely operate under load, so a visual inspection and checking the mechanics are more important.
☑️ Relay diagnostics
When replacing a relay, it is important to choose an analogue with identical characteristics. They differ in engine power and compressor type. Using the wrong relay may result in it not opening the starting winding circuit in time, causing the motor to overheat and burn out. Always check the markings on the old part with the new one before installation.
Malfunctions of the compressor windings and interturn short circuits
If replacing the relay did not help and the compressor hums and turns offthe problem may lie deeper - in the electric motor itself. The most serious malfunction is an interturn short circuit in the stator windings. In this case, the insulation of the copper wire is destroyed, and the turns are closed together. This leads to a sharp decrease in winding resistance and a multiple increase in current consumption, to which the thermal protection instantly responds.
You can diagnose an interturn short circuit using a multimeter by measuring the resistance between the motor contacts. In a working compressor, the resistance of the starting winding is usually higher than that of the working winding. If the device readings are chaotic, differ greatly from the passport data or show zero (short circuit), the compressor is faulty. Also a sign of a short circuit is the strong heating of the motor housing even after short operation.
Another problem is a break in the winding. In this case, the circuit does not close at all, and the engine does not hum, but simply makes a quiet relay click. However, a more common situation is when one of the windings “breaks through” onto the housing. You can check this by measuring the resistance between any contact and the compressor copper tube (housing). The device should show infinity. If there is at least some resistance, it means there is a breakdown to ground, which is dangerous for the user’s life.
| Type of fault | Winding resistance | Relay behavior | Sound signs |
|---|---|---|---|
| Normal | Working 10-20 Ohm, Starting 30-40 Ohm | Click at start, silence during operation | Smooth hum |
| Interturn short circuit | Significantly below normal | Instant shutdown | Humming and clicking |
| Winding break | Infinity | No reaction or click | Silence or single click |
| Breakdown to the housing | There is resistance with the housing | Tripping of an RCD or automatic machine | Humming or sparking |
Repairing a compressor with burnt windings at home is impossible. It requires rewinding the motor, which is not economically feasible, or replacing the entire unit. When installing a new compressor, it is necessary to replace the filter-drier and evacuate the system, otherwise the new motor will also quickly fail.
Problems with the starting capacitor
In some models of refrigerators, especially old or industrial ones, starting capacitoris used to start the engine. This element accumulates charge and releases it at the moment of start, creating the necessary phase shift. If the capacitor has lost capacity or has failed, the torque on the motor shaft is not enough to take off. The compressor tries to start, hums, but the rotor remains motionless.
A visually faulty capacitor often has a swollen housing, electrolyte leaks or traces of soot on the terminals. However, external integrity does not guarantee serviceability. You can check the capacitance only with a special device - a multimeter with a capacitance measurement function or a separate capacitor tester. If the actual capacity differs from the nominal capacity by more than 20%, the element must be replaced.
Is it possible to start a refrigerator without a capacitor?
Theoretically, you can try to start a motor with a powerful working winding manually (by unwinding the shaft), but this is a temporary and dangerous measure. Operating without a capacitor will cause the windings to overheat and burn out within minutes or hours. Operation in this mode is prohibited.]
Replacing a capacitor is a simple procedure, but requires compliance with polarity (if the capacitor is electrolytic) and correct voltage selection. Using a capacitor with a lower operating voltage will cause it to explode quickly. Always install a part with a voltage not lower than that specified on the original, usually 450V or 500V.
Mechanical compressor wedge and loss of compression
If the electrical part is good, the relay and capacitor are in order, and the refrigerator turns on for a few seconds and turns offthe cause may be mechanical. The piston group inside the sealed housing could jam due to oil production, metal shavings, or valve destruction. In this case, the engine is physically unable to turn the shaft, which is perceived by the system as an overload.
There is a “wedging” method, which sometimes helps to revive the engine. It consists of applying voltage to the working winding, bypassing the starting winding (only for a short-term jerk!) or mechanically acting on the body of a running motor. However, this method is only effective in 30% of cases and often gives only temporary results. If the compressor is stuck “tightly”, no traditional methods will help.
Another mechanical problem is loss of compression. The valves could burn out or break. In this case, the motor can run smoothly and for a long time without turning off, but there will be no cold. However, if loss of compression is accompanied by scoring in the cylinder, the motor may jam in certain positions of the piston, causing the protection to operate. This is a complex case that requires professional troubleshooting.
⚠️ Attention: Methods of starting a compressor bypassing the protection (direct 220V supply) are extremely dangerous. If the motor is actually jammed, such a start can lead to an explosion of the compressor housing or a wiring fire. Use these methods only if you are fully aware of the risks and do not plan to further operate the refrigerator in case of failure.
Malfunctions of the thermostat and control module
It happens less often that the reason for short cycles lies in the control system. If thermostat (the thermostat) is faulty, it may give incorrect signals to turn on and off. However, usually the thermostat simply does not allow the engine to turn on or does not allow it to turn off. The “on-off” scenario is not typical for a mechanical thermostat, unless its contacts are “stuck” in a state of vibration.
In electronically controlled refrigerators (No Frost, two-chamber with a display) is responsible for starting control module. Electronics can block the compressor from starting if the temperature sensors show an error, or if the self-diagnosis system detects too frequent starts. In this case, the refrigerator may go into emergency mode, pausing between startup attempts.
Checking the thermostat is simple: you need to close its contacts directly. If the refrigerator starts and operates normally when shorted, the thermostat is faulty. For electronic modules, diagnostics are more complicated and require checking error codes, which may be displayed on the display or by blinking indicators. Failures in the power supply of the module can also cause chaotic behavior of the entire system.
FAQ: Frequently asked questions
Is it possible to temporarily use the refrigerator if it turns on and off?
It is strictly not recommended. The products will not have time to freeze, which will lead to their spoilage. In addition, each startup cycle wears out the compressor. If the problem is in the relay, replacing it is inexpensive, but if the motor burns out, repairs will become economically unfeasible.
Why did the refrigerator start to click and turn off after defrosting?
Perhaps moisture got into the electrical contacts of the start relay or into the wiring. Also, during defrosting, tubes often break off or the defrost heater is damaged, which can cause a short circuit. Allow the unit to dry completely (24 hours) before turning it on.
How much does it cost to replace the starting relay?
The relay itself is inexpensive (from 500 to 1500 rubles depending on the model). However, calling a technician and doing the work may cost more than the part itself. If you know how to use a screwdriver and a multimeter, you can make the replacement yourself in 15 minutes.
It hums, but does not start - is it always the compressor?
No, most often it is the starting relay or capacitor. The compressor itself fails less often than its starting equipment. You should always start diagnostics by checking the relay, since this is the weakest and cheapest part of the circuit.