Situation, when the refrigerator stops cooling, and the compressor is silent or makes only a quiet hum, is familiar to many owners of household appliances. In most cases, the unit is not completely broken, but simply goes into protection mode due to a power surge or overheating. Understanding the principles of operation of protective automation allows you to quickly return the device to life without calling a technician. However, before starting any manipulations, it is necessary to clearly understand the difference between software blocking and mechanical jamming.
Modern models, be it Indesit, Bosch or LG, are equipped with complex electronic control boards that can block engine starting when anomalies are detected in the network. Older technology relies on mechanical thermal relays and triggers to reset controller errors and allow time for the thermal relay to cool down. If after this the humming does not stop or startup does not occur, more in-depth diagnostics will be required. It is critically important to completely de-energize the unit for at least 15-20 minutes before starting work.to reset controller errors and give the thermal relay time to cool down. If after this the humming does not stop or startup does not occur, more in-depth diagnostics will be required.
In this article we will analyze a step-by-step algorithm of actions for various types of compressors and control systems. You'll learn how to identify a faulty start relay, test motor windings, and safely bypass temporary lockouts to test the unit's functionality. Remember that working with electricity requires extreme caution and compliance with safety precautions.
Diagnostics of the compressor condition and identification of blockages
The first step in solving the problem is to accurately determine the symptoms. Users often confuse the normal operation of the system No Frost with a breakdown when the compressor simply rests in a pause between cycles. If the unit turns on, hums for a few seconds and clicks when it turns off, it means it has worked thermal protection or the starting relay cannot start the rotor. This is a classic sign that the engine is "blocked" by internal safety mechanisms.
For initial diagnosis, you will need a multimeter and access to the back of the refrigerator. Remove the compressor protective cover, which is usually secured with latches or screws. Visually inspect the wires for melting and check the temperature of the motor housing. If it is hot to the touch, and the refrigerator has not cooled for several hours, there is probably an insulation breakdown. sticking of contacts or insulation breakdown.
Pay attention to the nature of the sound when you try to start. A quiet hum without vibration indicates that current is flowing to the windings, but the rotor does not move. In this case, the start relay is often to blame. If there is a loud click and silence, the problem may lie in an open circuit or a malfunction of the relay itself. In rare cases, a characteristic knock is heard, which indicates mechanical destruction of the components inside the sealed casing.
⚠️ Attention: If the compressor housing has heated up to a temperature at which it is impossible to hold your hand for more than 2-3 seconds, further attempts to start without eliminating the cause may lead to a wiring fire or final failure of the engine. Allow the unit to cool completely.
Checking and replacing the starting relay
The starting relay is a small plastic block that fits onto the compressor contacts. It is this element that most often causes startup to be “blocked.” Inside it there is a coil or posistor, which wears out over time. If the relay does not close the starting winding circuit, the engine cannot gain speed and goes into protection. To check, carefully remove the relay by pulling it down or snapping the latches.
A visual inspection can immediately give the answer: the presence of burning, melted plastic or oxidized contacts indicates the need for replacement. If the element is externally intact, it can be checked with a multimeter in continuity mode. For posistor relays (often found in models Samsung and Atlant) the resistance should be low when cold and increase when heated. Electromagnetic relays should make a clear click when turned over.
Replacing a relay is a simple procedure and does not require special skills. The main thing is to buy exactly the same model, since they are designed for a specific engine power. An incorrectly selected relay may not start the compressor or, conversely, may not turn off the starting winding, which will lead to engine combustion. After installing the new element, try starting the refrigerator.
☑️ Checking the start relay
Resetting the error of the electronic control module
In refrigerators with an electronic control system (for example, many models Bosch, Siemens, LG) The compressor is controlled by the main module. During power surges in the network, the controller can detect an error and block the start of the compressor to prevent its combustion. In such cases, mechanical replacement of parts will not help until a soft reset is performed.
The standard reset procedure often looks like this: unplug the refrigerator for a long time, from 30 minutes to 2 hours. This is necessary so that the capacitors on the control board are discharged and temporary errors are erased from the memory. After turning on, the unit may conduct self-diagnosis for some time (up to 10-15 minutes), during which time the compressor may not start - this is normal.
If the error persists after a long de-energization, the control board itself or one of the sensors (temperature in the chamber, evaporator) may be damaged. Some models require entering the service menu to force the compressor to start. Commands for entering the service mode differ from manufacturer to manufacturer and often require simultaneously pressing several buttons on the control panel.
Examples of combinations for entering the service mode
For LG: simultaneously hold down the Freezer and Ice Plus buttons for 3-5 seconds.|For Samsung: hold down Fridge and Freezer at the same time for 8-12 seconds.|For Electrolux: hold down power button and temperature adjustment for 5 seconds.|Important: look for the exact combination for your model in the technical manual, since the firmware may differ.
It is worth noting that if the control module “sees” a short circuit in the compressor circuit, it blocks the voltage supply. In this case, it is necessary to ring the motor windings. If the resistance between the contacts shows zero or infinity, the module is right - the engine is faulty or broken into the housing.
Mechanical unlocking of a jammed engine
There is a phenomenon called “compressor wedge”, when the piston group gets stuck at a dead point due to oil production or mechanical wear. In this condition, the rotor cannot turn even when full voltage is applied. Sometimes the “wedging” method by applying increased voltage helps, but this method is risky and requires special equipment, such as starting device with a capacitor.
The essence of the method is to briefly apply 220V voltage directly to the working winding (bypassing the starting relay), sometimes using a starting relay capacitor. This creates a powerful magnetic impulse that can rip the pistons out of place. However, if the compressor is tightly jammed, this method can completely finish off the engine or lead to rupture of the pipelines inside the casing.
A safer, but labor-intensive method is to dismantle the compressor, turn it over and gently tap the housing with a wooden mallet in different directions. This can help dislodge stuck parts and redistribute oil. Sometimes it also helps to add a special composition to wash away deposits through the process pipe, but this requires a vacuum pump and refrigerant charging skills.
| Symptom | Probable cause | Solution method | Difficulty |
|---|---|---|---|
| Buzzes for 5-10 seconds, clicks, is silent | Faulty starting relay | Replace the relay | Low |
| Silent, no light, no errors on the display | Open circuit, no power | Checking the socket, cord, thermal fuse | Low |
| Humming constantly, not cooling | Freon leak, compressor wedge | Searching for leaks, replacing the compressor | High |
| Starts and immediately turns off | Thermal relay or interturn short circuit | Replacing a relay or motor | Average |
Checking the electrical circuit and thermal relay
Thermal relay (overload protection) is a bimetallic plate that opens the circuit when the compressor overheats. If it is faulty, it can open the circuit prematurely (too early), preventing the compressor from reaching operating mode. You can check it by ringing the contacts: in a cold state they should ring short (resistance is close to 0 Ohm).
It is also important to check the integrity of the supply wires. Vibration during operation of the refrigerator often leads to chafing of the insulation or burnout of the contacts on the terminal block. Oxidized contacts create additional resistance, causing heating and voltage drop, which is perceived by the system as an emergency situation. Cleaning the contacts and replacing the terminals often solves the problem of unstable starting.
If you find that the thermal relay is constantly tripping even when the engine is cold, this may indicate increased current consumption by the engine. This is a serious sign of worn windings or mechanical friction inside the compressor. In this case, replacing the relay will only have a temporary effect, followed by final failure.
⚠️ Attention: Never close the contacts of the thermal relay directly (“directly”) for testing or temporary operation. This removes the protection against overheating and can lead to a fire in the compressor in a matter of minutes.
When it is necessary to replace the compressor
There are situations when all unlocking methods have been exhausted, and the only solution is to replace the unit. If, when testing the windings, the multimeter shows an “open circuit” (infinite resistance) or a “short circuit” (resistance close to zero) to the housing, the motor is considered faulty. Also a sign of the death of the compressor is the lack of resistance between the common contact and the working/starting contact.
Another criterion is mechanical wear. If the compressor operates very noisily, with a metallic clanging sound, or its rod is loose (checked with the unit turned off by slightly shaking the pipes), the service life has expired. Attempts to revive such a unit are economically impractical and dangerous.
Replacing a compressor is a complex process that requires:
1. Taps of the old engine.
2. Installation of a new unit (it is important to choose an analogue in terms of power and refrigerant).
3. Replacing the filter drier.
4. Evacuation of the system.
5. Refilling with freon by weight.
It is almost impossible to carry out these operations independently without a vacuum pump, a pressure gauge station and the skills of soldering copper pipes. In this case, it is wiser to contact a service center, where they guarantee the tightness of the system and the correct dosage of the refrigerant.
Frequently asked questions (FAQ)
Is it possible to disassemble a hermetic compressor and repair it inside?
Theoretically this is possible, but in practice it is extremely difficult and impractical. To do this, you need to cut off the top cap, maintaining the geometry, find the fault (usually a broken valve or a cylinder scuff), replace the parts and then hermetically seal the housing back under pressure. The cost of such work and the risk of failure exceed the price of a new compressor.
Why is the refrigerator compressor hot, but does not start?
This indicates that current is supplied to the windings, but the motor cannot start rotating. The main reasons: jamming of the piston group, a malfunction of the starting relay (does not provide a starting impulse) or an interturn short circuit in the windings. It is also possible that the thermal relay is “stuck” in the closed state, but the engine is physically jammed.
How much does it cost to replace a compressor at the service?
The price consists of the cost of a new engine (from 3,000 to 10,000 rubles depending on the model) and the cost of work (from 4,000 to 8,000 rubles). The total amount is often 60-70% of the cost of a new refrigerator, so sometimes it is more profitable to buy new equipment.
Can low voltage in the network block the compressor?
Yes, at low voltage the motor consumes more current to create the required torque, which leads to rapid overheating of the windings and tripping of the thermal relay. Continuous operation in such conditions will shorten the life of the engine. It is recommended to use a voltage stabilizer.