Failure of the refrigerator to keep cold - this is always stress, which can lead to spoilage of a significant supply of food. Most often, the reason for a sudden stop of the unit is the failure of compressorwhich in everyday life is often called a motor or engine. It is this unit that is responsible for circulating the refrigerant through the system, creating the necessary pressure to cool the chambers. If you notice that the refrigerator is humming but not freezing, or is running silently and does not start at all, the first thing that comes to mind is to check the functionality of this key element.
Before calling a technician or buying a new unit, it makes sense to carry out an initial diagnosis on your own. This will allow you to understand the scale of the problem: whether a complex replacement of the unit is required or whether it is enough to change inexpensive parts of the trigger mechanism. To conduct a quality test, you will need a minimum set of tools, including a multimeter, as well as compliance with basic electrical safety rules. It is important to understand that compressor is a sealed unit, and if the problem lies inside its housing (an interturn short circuit or a wedge of the piston group), then it cannot be repaired, only replaced.
In this article we will analyze in detail the algorithm of actions that will help you determine the condition of the electrical part of the motor. We will look at how to measure the resistance of the windings, how to detect a breakdown on the housing and what to look for during a visual inspection. Competent diagnostics will save you time and money, giving you a clear understanding of whether it is worth undertaking repairs or whether it is easier to purchase new equipment.
Initial visual inspection and startup check
Any diagnostics begins with an external examination and analysis of the behavior of the equipment when trying to turn it on. If the refrigerator is silent, does not make any sounds and the light inside does not light, the problem may be trivial - lack of voltage in the outlet or damage to the power cord. However, if the lights are on but the engine does not start, or you hear a distinctive click followed by a hum that lasts a few seconds and then silence, this is a warning sign. In the latter case, starting relay tries to start the engine, but the compressor cannot gain speed due to a wedge or faulty windings.
Be sure to pay attention to the temperature of the compressor housing during operation or immediately after trying to start. If the motor is hot, but the refrigerator is not cooling, this may indicate that the shaft is jammed and the motor is running idle, overheating from the short circuit current in the windings. Also inspect the unit itself for mechanical damage, oil smudges or traces of burning, which may indicate a recent short circuit.
⚠️ Attention: Before starting any work on disassembling or testing contacts, be sure to disconnect the refrigerator from the power supply! Working with electrical appliances under voltage is deadly.
Often the cause of failure is not the motor itself, but the start-protection relay or thermal relay. These small plastic boxes are attached directly to the compressor housing. If, when shaken, the relay inside rattles like a rattle, it means that the contacts inside are burnt or destroyed, and the current simply does not reach the motor windings. Replacing this part is inexpensive and often solves the problem of a “non-working motor.”
Necessary tools for diagnostics
To properly check the motor refrigerator, you will need a specific but accessible set of tools. Without them, diagnostics will be of a mere nature, which is unacceptable when working with expensive equipment. The main device here is a multimeter (tester), which allows you to measure resistance and check circuits for breakdown.
- 🔧 Multimeter —the main device for measuring winding resistance and checking insulation.
- 🪛 A set of screwdrivers —for removing the back cover of the refrigerator and dismantling the compressor protective casing.
- 🧤 Dielectric gloves —to protect your hands when working with electrical components.
- 🔦 Flashlight —for better illumination of the work area in the area of the motor.
- 🧹 Clean rags —for cleaning contacts from dust and oxides before measurements.
The multimeter must be in good working order and have charged batteries, since even a small error in the readings can lead to an incorrect diagnosis. Before starting measurements, check the operation of the probes by connecting them to each other: the device should show zero or a value close to it. If you are using an analog (pointer) device, do not forget to calibrate it before work.
It may also be useful ohmmeterif your multimeter does not have a dialing function, although modern digital models fully cover this functionality. It is important that the tester probes are sharp and clean to ensure reliable contact with the compressor terminals, which are often covered with oxides or varnish.
Removing and accessing the compressor contacts
To get to the electrical terminals of the motor, It is necessary to provide physical access to the rear of the refrigerator. Usually the compressor is located in the lower niche, hidden behind a metal or plastic panel. Remove the back cover by unscrewing the mounting screws and move it to the side. You will see a view of a black cylindrical or spherical tank - this is the compressor housing.
A protective plastic box is installed on the motor housing, in which the starting and protective relays are located. It is under this cover that there are three contact pins coming out of the sealed compressor housing. Carefully remove the box from the relay. Often it is held on by latches or a clamp that needs to be released. Be careful not to damage the wires going to the relay.
After removing the relay, you will see three contacts arranged in a triangle. They can be marked with letters or symbols, but most often their location is standard for most models (for example Indesit, Atlant, Beko). Two contacts are closer to each other, and the third is separate. It is these findings that we will test with a multimeter to determine the condition of the windings.
☑️ Preparation for measurements
Testing the windings with a multimeter
The most reliable way to check the integrity of the electrical circuit inside the motor is to measure the resistance between the contacts. Switch the multimeter to resistance measurement mode (Ohm, limit 2 kOhm or 20 kOhm). First, find pair winding: call the contacts in pairs. Between two of the three contacts, the resistance should be minimal (usually from 10 to 30 Ohms) - this is the working and starting windings connected in series through a common point.
Then measure the resistance between each of these contacts and the third, free contact. Here the values should be higher since you are measuring the resistance of one winding relative to the other. Normal readings range from 20 to 150 ohms depending on the power and model of the compressor. If the device shows one (infinity) in any of the sections, it means that there has been an accident in the winding breakand the motor must be replaced.
A critically important step is checking for insulation breakdown (short circuit to the housing). Switch the multimeter to beep mode or to the maximum resistance limit (2 MΩ). Press one probe against any of the three contacts, and with the second touch a cleaned area on the metal body of the compressor (where there is no paint or rust). The device should not emit a beep, and the arrow or numbers on the screen should not change. If there is contact with the housing, operating such a motor is dangerous to life.
⚠️ Attention: If the resistance between the contacts differs significantly from the passport values (for example, it shows 0 Ohm or, conversely, infinity), this indicates an interturn short circuit or break. In this case, the compressor cannot be repaired.
For clarity, here is a table of typical resistance values for a working and faulty compressor:
| Measuring parameter | Normal value | Failure sign |
|---|---|---|
| Resistance between paired contacts | 10 - 30 Ohm | 0 Ohm (Short circuit) or ∞ (Open) |
| Resistance between contact and body | ∞ (Infinity) | Any value (Breakdown to the body) |
| Dispersion of readings between windings | No more than 20% | Strong difference (Interturn short circuit) |
| Response of the multimeter when continuity | Stable numbers | Jumping values (Bad contact) |
Why is it important to know the exact resistance?
Knowing the exact resistance values for your compressor model, you can identify an interturn short circuit at an early stage, when the motor is still running, but consumes increased current, which leads to network overload and frequent shutdowns of machines.
Checking the starting current and relay condition
If an electrical check of the windings did not reveal breaks or breakdowns, but the compressor still does not start, the problem may lie in the starting mechanism or mechanical jamming. For deeper diagnostics, professionals use a device for measuring inrush current (current clamp). However, at home, you can carry out an indirect test.
Remove the starting relay and carefully inspect its insides. If it is a relay with a posistor, check its integrity. If the relay is electromagnetic, check the mobility of the core and the condition of the contacts. Burnt contacts (black deposits, shells) prevent the normal flow of current, which is why the motor does not receive the necessary impulse to start. In such cases, replacing the relay often revives the refrigerator.
It is also worth mentioning the so-called “direct start” method, which is sometimes used by experienced craftsmen to test the ability of the motor to start without a relay. This method is dangerous and requires the use of a special start button and short circuit protection, so it is not recommended for repetition by untrained users. The essence of the method is to briefly apply voltage directly to the starting winding. If the motor starts and works, the problem is in the relay; if it hums and does not spin, a wedge is likely.
It is important to consider that the location of contacts and types of relays may differ from manufacturer to manufacturer. For example, compressors Danfoss (Secop) have a design that may differ from the usual asymmetrical models. Always check the technical documentation or the diagram printed on the sticker of the compressor itself, if it is preserved.
Frequent errors when diagnosing the motor
When independently checking refrigeration equipment, beginners often make mistakes that can lead to false conclusions or even damage to the equipment. One of the most common mistakes is taking measurements on a device connected to the network. This is not only dangerous, but also useless, since a multimeter in ohmmeter mode can burn out from a voltage of 220V.
Another mistake is ignoring the condition of the wires. It often happens that the compressor itself is working, but the wiring going to the terminals is burnt out or oxidized. Before drawing conclusions about a motor malfunction, make sure that the wires are intact and the contacts on the relay connectors are clean and not loose. Oxides can create a high contact resistance, which the multimeter will perceive as a break.
- 🚫 Measurements under voltage — are strictly prohibited when checking resistance.
- 🚫 Dirty probes — oxidized probe contacts give a large error.
- 🚫 Ignoring the temperature —the resistance of the windings depends on the temperature; a cold and “hot” motor may show different values.
- 🚫 Forced start without protection —an attempt to start the motor with a screwdriver or twist without a relay can lead to a fire.
Also, do not forget that a modern refrigerator is a complex system where an electronic control module may be responsible for starting the motor. If your model does not have a classic relay, but has an electronic board, the diagnostics shift towards checking signals from the board to the compressor. In such cases, it is better not to experiment without an oscilloscope and deep knowledge of electronics.
⚠️ Attention: The characteristics of refrigerators and control circuits may vary depending on the year of manufacture and model. Always check the electrical diagrams in the official service manual for your specific equipment, since there are no universal solutions for all brands.
Diagnostic results and further actions
To summarize, we can say that checking the refrigerator motor is a process of eliminating faults. If the multimeter shows a break or a breakdown in the housing, the compressor is dead and requires replacement. If the windings are intact, but the motor does not start, we change the relay. If the relay is working properly, and the motor is humming and standing still, most likely, a mechanical wedge has occurred, and only replacing the unit or professional repairs with opening the housing (which is not economically feasible) will help here.
Replacing a compressor is a complex technical procedure that requires a vacuum pump, a pressure gauge station, a burner, and skills in working with copper pipes and refrigerant. It is almost impossible to replace the motor and refill the system with freon on your own, without equipment. Therefore, if diagnostics confirmed the death of the motor, the best solution would be to call a technician.
Nevertheless, self-diagnosis allowed you to save money on a technician’s visit to establish the fact of a breakdown and gave you an understanding of the situation. Now you know what exactly happened, and you can reasonably communicate with the service center, understanding what exactly you are paying for.
Is it worth repairing an old refrigerator?
Repairing an old refrigerator with replacing the compressor is often not economically justified, since the cost of a new motor and work can be up to 70% of the price of a new unit.
Is it possible to check a compressor without a multimeter?
It is impossible to qualitatively test a compressor without a multimeter. You can only indirectly judge its condition by sound and heating, but it is impossible to determine a break in the winding or a breakdown in the housing without a device. Attempts to connect the motor directly to the network without checking are fraught with knocking out the plugs or a fire.
Why is the compressor hot, but the refrigerator does not freeze?
This may indicate several problems: a clogged capillary system, a freon leak, or a malfunction of the compressor itself (valves). If the motor is hot and humming, but does not start fully, it is probably jammed or the starting winding has burned out.
How many ohms should there be on a working compressor?
Resistance in the range from 10 to 30 ohms between paired contacts and up to 150 ohms between other pairs is considered normal. The main thing is the absence of infinity (break) and zero (short circuit), as well as the absence of contact with the body.
What to do if the resistance of the windings is different?
If the resistance of one of the windings differs significantly from the other (more than 20-30%), this is a sign of an interturn short circuit. Such a compressor will operate unstably, overheat and soon fail. Replacement is recommended.