A sudden breakdown of the refrigerator is always stress, because food supplies and the comfort of household members are at risk. One of the main symptoms of a serious malfunction is a working but not cooling unit, or complete silence of the equipment when plugged into the network. In most of these situations, suspicion falls on compressorwhich is often called the “heart” of the refrigeration system. It is this unit that is responsible for the circulation of the refrigerant, and if it fails, the entire cooling cycle is disrupted.
Before calling a technician or buying a new refrigerator, it makes sense to conduct an initial diagnosis. This will help you understand the scale of the problem: perhaps the problem is in the starting relay or thermostat, but the motor itself is intact. However, if diagnostics indicate interturn closure or a break in the windings, repairs may not be economically feasible. In this article, we will examine in detail the testing methods that will allow you to independently assess the condition of the motor.
It is worth immediately noting that any work with electrical appliances requires compliance with safety precautions. You will have to deal with 220 volt electric current, so neglecting the rules can lead to serious consequences. If you are not confident in your abilities or do not have basic skills in working with a multimeter, it is better to entrust this procedure to professionals.
Primary diagnostics without tools
You should start checking with an external inspection and analysis of the behavior of the refrigerator. Often the characteristic signs of a compressor malfunction can be noticed without the use of complex equipment. First of all, pay attention to how start relayhe behaves. If, when you turn on the refrigerator, you hear a loud click, followed by the hum of the motor, and then again a click and silence, this is a sure sign that the engine is trying to start, but cannot.
The second important indicator is the temperature of the case. During normal operation, the compressor heats up, but if it becomes too hot to touch, this may indicate overheating due to a seized piston group or an electrical problem. It is also worth checking for the absence of a burning smell, which often appears when winding insulation burns.
⚠️ Attention: If you smell burning plastic or see sparking in the motor connection area, immediately unplug the refrigerator. Further attempts to turn on may lead to a fire.
The third sign is idle operation. The motor hums continuously, without turning off for hours, but the temperature inside the chambers does not drop. This may indicate a loss of compressor performance when it is running but does not create the necessary pressure to circulate freon. In such cases, replacement of the unit is often required, since it is impossible to restore tightness and power at home.
Do not forget that a visual inspection should include checking the integrity of the wires going to the motor. Melted insulation or blackened contacts can cause a false diagnosis. Sometimes the problem lies not in the motor itself, but in poor contact, which is easy to fix.
Required tool for testing
To carry out high-quality and safe diagnostics, you will need a minimum set of tools. Without them, the check will be superficial and will not give an accurate answer about the technical condition of an electric motor. The main device in a home craftsman's arsenal should be a multimeter (tester). This universal device allows you to measure resistance, voltage and circuit integrity.
In addition to the multimeter, you will need:
- 🔧 A set of screwdrivers (phillips and flat) for removing the casing.
- 🔌 Pliers for careful removal of terminals.
- 🧤 Dielectric gloves for protection against accidental electric shock.
- 🔦 Flashlight for illuminating hard-to-reach places in the compressor niche.
It is important that the multimeter probes are in good working order, and the device itself has a charged battery. A low-quality tool may show false results, leading to erroneous conclusions. Before starting work, be sure to check the tester on a known working circuit, for example, on a battery or socket (being careful).
It is also worth preparing a clean rag to wipe the contacts from dust and oxides. Dirt on the terminals can significantly distort resistance readings, creating the appearance of an open or short circuit where there is none. Clean contacts are the key to accurate diagnostics.
Dismantling and access to the electrical part
To get to the compressor terminals, you need to remove the rear protective cover of the refrigerator. It is usually secured with several screws or latches. Before starting work, the refrigerator must be disconnected from the power supply! This is a critically important safety rule, the violation of which is unacceptable.
After removing the cover, you will see a black cylindrical or pear-shaped tank - this is the compressor. On its body there is a box containing a starting and protective relay, as well as a capacitor. It is this box that must be carefully removed in order to gain access to the motor contact group.
☑️ Removal procedure
When removing the terminal block, be careful: the wires can be hard from time and heat. Do not pull them with force so as not to break them. It is better to slightly loosen the connector or pry it off with a flat screwdriver. Removing the relay cover will reveal three compressor terminals arranged in a triangle.
These terminals are usually marked or color-coded, but over time the markings can wear off. The standard connection diagram includes a common terminal, a working winding and a starting winding. Understanding which pin is responsible for what is necessary to correctly measure resistance.
Checking the windings with a multimeter
The most reliable way to determine the health of the motor is to ring its windings. There are usually three terminals on the contact group. To understand which one is which, you need to measure the resistance between all pairs of contacts. Set the multimeter to resistance measurement mode (Ohms) to a limit of 200 Ohms.
Measure the resistance between each pair of contacts. You will get three values. The sum of the two smaller values must equal the largest value. For example, if between contacts A-B there are 20 Ohms, B-C 50 Ohms, and A-B 70 Ohms, then 20 + 50 = 70. In this circuit, the contact common to two smaller resistances (B in our example) is common output.
Next we distribute the roles:
- 📏 The pair with the least resistance is the working winding and the common wire.
- 📏 The pair with the highest (but not maximum) resistance is starting winding and the common wire.
- 📏 The pair with maximum resistance is the ends of the starting and working windings.
Normal resistance values depend on the power of the motor and usually range from 10 to 50 Ohms for the working winding and from 20 to 100 Ohms for the starting winding. If the multimeter shows one (infinity) in any of the measurements, this means a winding break. If it shows zero, there is a short circuit. In both cases, the compressor is faulty and requires replacement.
Why is it important to know the resistance of the windings?
Knowing the normal resistance helps to distinguish a working motor from a burnt one. If the resistance is very different from the passport data (for example, 2-3 Ohms instead of 30), this is a sign of an interturn short circuit. A motor with such a malfunction will get very hot and knock out the circuit breaker.
Diagnostics for breakdown of the housing
Another dangerous malfunction is breakdown of the insulation of the windings on the housing. In this case, the motor can work, but touching the metal parts of the refrigerator becomes deadly. To check this malfunction, the multimeter switches to the continuity mode or resistance measurement to the maximum limit (2 MOhm).
One probe is applied to any of the three contacts on the compressor (possibly a common one), and the second to a cleaned place on the metal motor body (where there is no paint or rust). If the device shows a resistance of less than 2 megohms or makes a beeping signal, then the insulation is broken.
| Measurement type | Normal reading | Fault indication | Diagnosis |
|---|---|---|---|
| Working winding | 10 – 50 Ohm | 0 Ohm or ∞ (infinity) | Short circuit or open circuit |
| Start winding | 20 – 100 Ohm | 0 Ohm or ∞ (infinity) | Short circuit or open circuit |
| Winding - Housing | ∞ (infinity) | Any value | Breakdown on housing |
| Thermal relay | 0 Ohm (closed) | ∞ (open) | Faulty relay |
A breakdown on the housing is an unambiguous verdict compressor. It is impossible to operate such a refrigerator, as it threatens people’s lives. Even if it continues to freeze, the risk of electric shock when touching the body or food inside (if the insulation of internal elements is broken) is too great.
Sometimes the breakdown can be “floating” and appear only when heated. Therefore, if in doubt, it is better not to take risks. The only safe way to eliminate a breakdown in the housing is to completely replace the compressor, since windings are not rewinded at the factory for household refrigerators.
Checking the start relay and thermal protection
Often the compressor itself is working, and the problem lies in the starting device. The starting relay is responsible for briefly supplying voltage to the starting winding to start the engine. Thermal protection (thermal relay) turns off the motor when it overheats. These elements are located in the same plastic box that we removed earlier.
The relay is checked visually and “by sound”. Shake the relay: if it rattles inside, it means the core or contacts are broken and need to be replaced. Also, the contacts could burn out. You can check the integrity of the relay circuit with a multimeter in continuity mode. The resistance of a working relay should be close to zero.
⚠️ Attention: Starting relays come in different types (induction, posistor). They are not always interchangeable. When purchasing a new part, be sure to check the model with the original or use the correspondence table.
Thermal protection is also checked by continuity. When cold, it should ring (resistance 0 Ohm). If the circuit is open when the relay is cold, it is faulty. However, if the relay has tripped due to overheating, it takes time (10-15 minutes) to cool down for the contacts to close again.
Replacing these elements is inexpensive and often brings the refrigerator back to life. The main thing is to install them correctly on the compressor contacts so that they fit tightly and do not spark during vibration.
Frequent questions and answers (FAQ)
Is it possible to start a compressor without a relay?
Technically, you can start the motor by applying voltage directly to the working and starting windings, but doing this at home is extremely dangerous and not recommended. This requires precise knowledge of the time at which the pulse is applied to the starting winding. Incorrect starting can lead to instantaneous burnout of the windings or injury.
You hear a clicking sound, but the compressor does not start - is this definitely the motor?
Not necessarily. The thermal relay makes a clicking sound, cutting off the power. This could be due to a stuck compressor, faulty start relay, low voltage, or a broken thermostat. A comprehensive diagnosis of all circuit elements is required.
What is the service life of the compressor?
The average service life of modern compressors is 10-15 years with proper operation. However, frequent voltage fluctuations, overheating and insufficient ventilation of the rear wall can reduce this period by half.
Is it worth changing the compressor yourself?
Replacing a compressor requires not only electrical knowledge, but also skills in working with the refrigeration circuit (evacuating, filling with freon, soldering copper pipes). Without special equipment and a license to work with refrigerants, such work cannot be performed efficiently. This is a task for the service center.
Why does the new compressor get hotter than the old one?
Modern models may have different thermal characteristics. However, if only the top part heats up or the temperature exceeds 90 degrees, this may indicate improper freon charging or air in the system. A check of the pressure in the circuit is required.