A sudden stop of operation of the refrigerator or the appearance of an extraneous hum often indicates problems with the heart of the unit - compressor. It is this unit that is responsible for circulating the refrigerant in the system, creating the necessary pressure to cool the chambers. When the equipment stops freezing and the inside becomes warm, the first thing owners tend to do is to blame the electronics or a freon leak, forgetting about the motor.
However, before calling a technician or buying a new unit, it is worth carrying out basic diagnostics yourself. This will allow you to understand the scale of the problem: is a complex replacement of the unit required or is it enough to change an inexpensive part like starting relay. A competent check will help save significant money and time.
In this article we will analyze in detail the algorithm of actions for identifying electric motor faults, explain how to use a multimeter to measure the resistance of the windings and what symptoms you should pay special attention to. You will find out in which cases repair makes sense, and when it is easier to replace the entire unit.
Primary diagnostics and visual inspection
Before disassembling the back panel and taking up tools, it is necessary to conduct an external inspection and analysis of the behavior of the refrigerator. Often, characteristic signs can indicate a problem even before measurements are taken. Pay attention to how the equipment behaves in operating mode.
If you hear that the engine is trying to start, makes a humming sound, clicks, but stalls after a few seconds, this may indicate a jammed piston group or a malfunction of the starting mechanism. Normally, the compressor should turn on relatively quietly and operate evenly.
⚠️ Attention: Before starting any diagnostic work, be sure to disconnect the refrigerator from the electrical network! Working with live electrical wiring is deadly.
It is also worth checking the temperature of the compressor housing itself. If it is hot to the point that it cannot be touched, this may indicate overheating of the windings or thermal breakdown. At the same time, an absolutely cold motor with the backlight on and the thermostat on indicates that electricity simply does not flow to it.
Necessary tools for testing
For high-quality diagnostics, you will need a minimum set of tools, which most home craftsmen can find. The main device will be multimeter (tester), which allows you to measure resistance and check the integrity of the circuit.
In addition to the measuring device, prepare screwdrivers for removing the protective casing at the bottom of the refrigerator. In some models Indesit or Atlant a wrench may be required to unscrew the nuts, but most often a Phillips screwdriver is sufficient.
☑️ Preparing for diagnostics
It will not be superfluous to have pliers on hand for carefully removing the terminals and insulating tape in case you need to insulate the wires. A flashlight is also useful, since there is usually no lighting in the niche of the compressor compartment.
Checking the serviceability of the starting relay
Often the problem lies not in the engine itself, but in the starting relay, which provides an impulse to start the motor. This small unit attaches directly to the compressor housing and has three contacts. Its malfunction is one of the most common reasons why the refrigerator hums but does not start.
To check the relay, it must be carefully removed from the compressor contacts. Usually it is fixed with a bracket or simply put on the terminals. After removal, inspect the housing for melting, cracks or burn marks. If a ringing sound is heard inside when shaken, it means that the internal mechanism is destroyed.
Ring the relay contacts with a multimeter in resistance measurement mode. Depending on the design (electromagnetic or thermal), resistance must either be present or absent in certain combinations. If the device shows infinity where there should be a circuit, the relay must be replaced.
How to determine the type of relay?
Electromagnetic relays are usually heavier and have one winding, thermal ones are lighter and work on the principle of a bimetallic plate. For different types LG or Beko different relay models are suitable.
The cost of a new relay is low, and replacing it often solves the starting problem without the need to intervene in the system of the compressor itself. This is the simplest and cheapest repair option.
Measuring winding resistance with a multimeter
The most reliable way to check the condition of an electric motor is to measure the winding resistance. To do this, you need to gain access to the contact group of the compressor by removing the protective cover and disconnecting the wires.
The contact connector usually has three pins. Two of them correspond to the working and starting windings, and the third is common. You need to ring these contacts in pairs, measuring the resistance between them. The measurement results will allow you to judge the integrity of the windings.
Normal resistance values may vary depending on the power and model of the engine, but usually they are in the range from 10 to 60 ohms. If the device shows one (infinity), this means an open circuit. If the resistance is close to zero, there is a short circuit.
If the values are equal or differ slightly, this may indicate an interturn short circuit, which is a serious malfunction.
Table of normal indicators and malfunctions
For ease of interpretation of the data obtained, check the table below. It will help classify the condition of the compressor based on the multimeter readings.
| Measurement parameter | Normal value | Malfunction symptom | Probable cause |
|---|---|---|---|
| Resistance windings | 10–60 Ohm (depending on the model) | Infinity (1) | Open winding circuit |
| Resistance between terminals | Miscellaneous for starting and operating | About 0 Ohm | Short circuit |
| Resistance to body | Infinity | Any value | Insulation breakdown on the case |
| Case temperature | Warm (40–60°C) | Very hot or cold | Overheating or failure to start |
Pay special attention to checking for breakdown on the housing. To do this, one multimeter probe is applied to any contact of the connector, and the second to a cleaned place on the metal body of the compressor (you can slightly scratch the paint for better contact).
If the device shows at least some resistance, it means that the insulation is broken, and the operation of such a refrigerator is life-threatening. In this case compressor requires immediate replacement; it cannot be repaired.
Direct connection and starting check
If the electrical parameters of the windings are normal, but the refrigerator still does not start, you can try to apply voltage directly, bypassing the starting voltage relay and thermostat. This method requires caution and an understanding of the principles of operation of electrical circuits.
For this, a special cord with a plug is used, the ends of which are stripped. One end is connected to the common terminal, and the other is briefly shorted to the start terminal to simulate the operation of a relay. If the motor starts and runs smoothly, then the problem was in the control circuit.
⚠️ Attention: When connected directly, the compressor can operate under high pressure without protection. Do not keep it turned on for more than 5–10 minutes to avoid overheating and rupture of the tubes.
During such testing, listen carefully to the operation of the motor. Extraneous metallic knocking, clanging or excessive vibration may indicate mechanical wear of the piston group or valves. In this case, even an electrically serviceable engine will not be able to ensure normal circulation of freon.
Mechanical faults and jamming
Sometimes the electrical part is fully operational, but the compressor does not start due to mechanical jamming. This can happen due to oil burnout, moisture entering the system, or natural wear of rubbing parts.
You can try to wedge the engine using the so-called “beating”. To do this, gently strike the body of a working (under voltage) or just turned off compressor with a wooden mallet or the handle of a hammer. Vibration sometimes helps to move stuck pistons.
However, this method does not always help and is temporary. If after several attempts the motor does not come to life, it most likely needs to be replaced. Operating a jammed unit will only lead to burnout of the windings.
It is also worth checking the condition of the mounting shock absorbers. If they are destroyed, the vibration of the running motor will be transmitted to the body of the refrigerator, creating a strong noise, which can be mistaken for a malfunction of the compressor itself.
Frequently asked questions (FAQ)
Is it possible to replace the compressor yourself?
Theoretically, yes, but this requires special equipment: a vacuum pump for pumping out air and a station for refilling freon. Without sealing the system and vacuuming, the refrigerator will not work, so it is better to entrust the replacement to professionals.
Why is the compressor hot, but the refrigerator does not freeze?
This may indicate a refrigerant leak or blockage of the capillary system. The engine idles, trying to build up pressure, but there is no gas circulation. Failure of the valves inside the compressor is also possible.
How long does a compressor last on average?
The service life of modern compressors, especially inverter models Samsung or LG, can reach 10–15 years or more. Conventional linear motors last about 7–10 years, depending on operating conditions.
What to do if the multimeter shows a short circuit?
If the resistance between the contacts is close to zero, then an interturn short circuit of the windings has occurred. Such a compressor cannot be repaired, it must be disposed of and replaced with a new one.