The situation when the refrigerator stops cooling and food begins to spoil always takes you by surprise. First of all, many owners of household appliances begin to suspect the failure of the most expensive part - compressor. It is this unit that is responsible for circulating the refrigerant in the system, creating the necessary pressure to remove heat from the chambers.
However, do not rush to call a technician or buy a new unit, since often the problem lies in less significant elements, such as a start relay or thermostat. Competent primary diagnostics allows you to understand the scale of the problem and make a decision on the advisability of further repairs. In this article we will analyze proven methods for assessing the condition of the motor.
There are several checking methods, from simple visual inspection to the use of specialized equipment. It is important to understand that the compressor is the heart of the refrigerator, and its incorrect operation can be caused by both electrical and mechanical factors. Modern inverter models require a special approach that differs from the diagnosis of classic linear motors.
Primary diagnostics without tools
Before disassembling the unit or looking for measuring instruments, it is worth conducting a basic analysis of the operation of the device. Plug in the refrigerator and listen to the sounds it makes. A working one usually emits a smooth, low-frequency hum, which can be interrupted when stopping or starting. If you hear loud clicks, a hum that ends abruptly, or complete silence when the power is turned on, these are the first signs. compressor usually emits a smooth, low-frequency hum that may be interrupted when stopping or starting. If you hear loud clicks, a buzzing sound that ends abruptly, or complete silence when the power is turned on, these are the first signs.
Visually inspect the back wall of the refrigerator. Heating of the capacitor grid (usually black) is an indirect sign of system operation. If the motor hums, but the grill remains cold for an hour, there may be a freon leak or a capillary tube blockage, and the motor itself is idling.
⚠️ Attention: If you smell a burning smell or see sparking in the compressor area, immediately unplug the appliance from the power supply. Further operation may lead to a fire or complete burnout of the wiring.
It is also worth checking the temperature of the compressor housing itself. Gently touch the metal casing with the back of your hand. If it is hot to the point where it is impossible to hold your hand, or, conversely, absolutely cold when the engine is running, this indicates serious problems. Overheating often indicates an inter-turn short circuit of the windings, and a cold body when buzzing indicates jamming of the piston group.
Checking the start relay and thermostat
Often the reason that the compressor does not start or turns off after a few seconds is not the engine itself, but its “piping.” Start relay is responsible for sending a starting pulse to the winding, and the thermostat (or temperature sensor) gives the command to turn on. If the relay is stuck or burnt out, the motor will not receive the necessary push to start.
To check the relay, you need to remove the back cover of the compressor and carefully remove the plastic box placed over the contacts. Shake it near your ear: if you hear ringing or knocking inside, it means the contacts are burnt or the mechanism is destroyed. In this case, replacing the relay can completely solve the problem without interfering with the electrical part of the engine.
The thermostat is also easy to check. Connect the two wires coming from the thermostat to each other (after disconnecting the refrigerator from the network!). If the compressor starts working after being plugged in, it means that the temperature sensor is faulty. This is a common problem in older models where the mechanics wear out.
☑️ Diagnostics of the start relay
Using a multimeter to check the windings
The most accurate diagnostic method is to check the resistance of the windings using multimeter. This device allows you to determine the integrity of the electrical circuit and the absence of short circuits. Before starting work, make sure that the refrigerator is unplugged and the terminal block is removed from the compressor.
Most compressors have three terminals: two for the working windings and one common. Switch the multimeter to resistance measurement mode (Ohms) and take measurements between pairs of contacts. Normal readings should range from 10 to 30 ohms for the operating winding and slightly higher for the starting winding. If the device shows infinity (open circuit) or zero (short circuit), the compressor is faulty.
Pay special attention to checking for breakdown on the housing. Press one multimeter probe to the cleaned area on the compressor housing (where there is no paint), and touch each of the three contacts with the other. The device should show infinity. Any resistance value indicates that the insulation of the windings is broken and the motor is “breaking through” to ground.
| Measurement parameter | Normal value | Fault symptom | Probable cause |
|---|---|---|---|
| Starting winding resistance | 20–40 Ohm | Infinity or 0 Ohm | Open or short circuit turns |
| Working winding resistance | 10–25 Ohm | Significantly higher than normal | Burning of contacts |
| Resistance between windings | Sum of resistances | Mismatch sum | Circuit violation |
| Case resistance | Infinity | Any numerical value | Insulation breakdown |
In such cases, a standard test with a multimeter may not be informative enough.
Why can the multimeter readings “jump”?
If, when measuring resistance, the numbers on the multimeter screen are unstable, this may indicate poor contact of the probes or the presence of oxides at the terminals. This is also typical for compressors that have recently been running and have not yet cooled down, since the resistance of copper depends on temperature. Allow the unit to cool completely before taking measurements.
Analysis of current consumption (Current clamps)
If the electrical resistance of the windings is normal, but the compressor still does not start or does not work correctly, it is necessary to measure the current strength. For this purpose current clampsare used. This method allows you to estimate the real load on the engine during operation, which cannot be done with a conventional tester.
Connect the refrigerator to the network through an adapter that allows you to get close to one of the supply wires, or use a special plug with separated contacts. At the moment of starting, the current increases briefly (inrush current) and then drops to the rated value. For household refrigerators, the operating current is usually from 0.5 to 1.5 Amperes, depending on the power and model.
If the current significantly exceeds the rated current (for example, 3-4 Amperes and above), this indicates a difficult start, jamming of the mechanism or an interturn short circuit, which was not determined when checking the resistance. If the current is close to zero, but there is a hum, it means that the rotor cannot move due to mechanical blocking.
⚠️ Attention: Current measurements are carried out under a voltage of 220 Volts. Be extremely careful not to touch exposed wires with your hands and use a tool with the appropriate electrical safety class.
Compare the data obtained with the information on the compressor nameplate. The rated current (RLA - Rated Load Amps) is always indicated there. Exceeding this value by more than 20-30% is critical and requires stopping the unit.
Mechanical causes of compressor failure
The problem does not always lie in the electrics. The mechanical part of the compressor is a complex system of pistons, valves and bearings operating in a sealed circuit. One of the common causes of failure is seizing piston group. This occurs when the oil loses its properties or its level becomes critically low due to leaks.
Another common mechanical problem is a broken connecting rod or damaged valves. In this case, the compressor may hum, creating vibration, but not build up pressure. It is difficult to check this without opening the case, but an indirect sign is the absence of heating of the condenser and the same pressure in the system (if a pressure manifold is connected).
Vibration may also indicate wear on the internal shock absorbers of the engine suspension. If the motor is “dangling” inside the casing, it can touch the walls, creating a metallic clang. In the long term, this will lead to depressurization of the casing and leakage of freon.
Specifics of diagnostics of inverter models
Modern refrigerators with the inscription Digital Inverter or Linear Inverter are designed fundamentally differently. They do not have a classic start relay, and the start and speed control are carried out by an electronic module. Testing such a compressor with a conventional multimeter often gives false results, since the windings may sound the same.
To diagnose inverters, a special tester or module operation simulator is required. Often the compressor itself is fine, but the problem lies in the control board, which does not produce the necessary pulses. An error on the refrigerator display (for example, Samsung or LG error codes) often indicates a failure in communication between the module and the motor.
If the inverter compressor makes strange sounds or jerks when trying to start, first check the voltage at the output of the inverter board. The absence of a stable signal indicates a malfunction of the electronics, not the engine itself. Replacing an inverter motor is an expensive procedure, so the accuracy of the diagnosis is critical here.
Frequently asked questions and answers (FAQ)
Can the compressor work, but not to refrigerate?
Yes, this is possible. If the compressor hums and vibrates, but does not create the necessary pressure (for example, due to broken valves or freon leakage), there will be no cold in the chambers. The motor idles, overheats, but the cooling cycle does not complete.
How long should the compressor operate normally?
The operating time depends on the refrigerator load, room temperature and settings. Typically the operating cycle ranges from 10 to 30 minutes, followed by a pause. If the motor runs non-stop for hours, this is a sign of a malfunction (leakage, wear, problems with the thermostat).
Is it dangerous to open the compressor yourself?
It is strictly not recommended. Inside there is refrigerant under pressure, as well as oil vapor. In addition, professional equipment is required for hermetically sealed back. Self-opening makes further repairs economically unfeasible.
Why does the compressor click and not start?
Most often this indicates a faulty start relay or a jammed engine. The relay tries to start the engine, clicks, but due to the lack of start, the protection is triggered and opens the circuit. The cycle is repeated until the part cools down or the part is replaced.