The situation when the refrigerator stops freezing, but there is silence inside or, conversely, there is a hum without starting, always takes you by surprise. First of all, owners begin to suspect the most expensive and complex thing - compressor. Indeed, this particular unit is the heart of the system, ensuring the circulation of the refrigerant. However, it is too early to rush to conclusions about a fatal breakdown and immediate replacement of the unit, since often the problem lies in related elements, such as a start relay or thermostat.
Before grabbing the tools, it is necessary to carry out primary visual and auditory diagnostics. If you hear a distinctive click, followed by a hum that lasts a few seconds, and then another click and silence, this is a classic sign that engine tries to start, but something is preventing it. This could be jamming of the piston group, failure of the starting winding, or a banal lack of freon, although the latter is less common with such symptoms. Understanding the nature of sound helps you narrow down your search and avoid making mistakes during further disassembly.
For accurate diagnostics, you will need a minimum set of tools that any home craftsman will have: a multimeter, screwdrivers and pliers. It is important to understand that checking the electrical circuit is only part of the process. It is difficult to determine the mechanical condition of the piston group without opening the compressor housing (which is strictly forbidden to do on your own), but indirect signs will help you make the right decision. In this article we will look at how to distinguish a burnt winding from a faulty relay and when repairs are really necessary.
Safety when working with electrical appliances comes first. Any manipulations with the electrical components of the refrigerator must be carried out only when the power is disconnected from the mains. Even a short-term touch of live parts under voltage can lead to serious injuries, so do not neglect this rule even for a second.
External inspection and initial diagnostics without tools
The check should always begin with an external examination, since many faults are visible to the naked eye. Carefully inspect the back wall of the refrigerator in the compressor area. If you find traces of soot, melted plastic on the motor housing or blackened wires, this is a sure sign interturn short circuit or overheating. In such cases, further diagnostics may no longer be necessary - the unit requires replacement.
Pay attention to the tubes coming out of the compressor. When the engine is running (if it does start), one of the tubes (discharge) should be hot, and the other (suction) should be cold or even covered with frost. If the compressor is working, but both tubes have the same temperature, this may indicate a loss of compression. Piston group It could have worn out so much that pressure in the system is not created, and the refrigerant simply circulates without changing the state of aggregation.
⚠️ Attention: If when you touch the compressor housing you feel a strong vibration or hear a metallic knock, this may indicate destruction of the internal engine mount. Operation of such a refrigerator will lead to complete destruction of the mechanism in the shortest possible time.
It is also worth checking the condition of the wiring. Often the wires rub against the vibration tubes or housing, which leads to a short circuit. Inspect the contacts for oxidation. Green or white deposits on the terminals increase resistance and may prevent normal starting. Stripping the contacts sometimes solves the problem if the electric motor electric motor itself is in good order.
Checking the starting and protective relay
One of the most common reasons why the refrigerator does not turn on is a malfunction of the starting relay. This small element is responsible for supplying voltage to the starting winding at the moment of start and then turning it off. If the relay is stuck or burned out, the compressor will not receive the necessary impulse to start. Visually, there should be no cracks on the relay, and when shaken, a working element should not make rattling sounds (if there are dangling parts inside, the mechanism is damaged).
The protective relay, which is often combined with the starting one in modern models, serves to turn off the power in case of overheating or overcurrent. If it is faulty, the circuit may be permanently broken. To check, you need to remove the relay from the compressor. Usually it is fixed on three contacts and is held in place by a spring clip or latches. Carefully remove it, being careful not to damage the contacts.
The relay is checked with a multimeter in dial mode. It is necessary to “ring” the contacts in different positions. In normal condition, the chain should ring. If the device shows a break (one on the digital display or no sound signal), then the element is faulty. It is also worth checking the thermoelement (bimetallic plate) - when it heats up, it should open the circuit, and when it cools down, close it again.
- 🔌 Contacts: Check for deposits on the relay contacts, which can prevent the flow of current.
- 🔨 Mechanics: Make sure that the moving parts the relay is not stuck in one position.
- 🌡️ Thermal protection: Check the resistance of the thermoelement - it should be close to zero in a cold state.
If the relay is working properly, but the compressor still does not start, the problem is most likely everything, deeper. However, replacing the relay is the cheapest and easiest repair and often brings the refrigerator back to life. The cost of a new relay is not comparable to the price of a new compressor, so it’s worth starting diagnostics with it.
Diagnostics of compressor windings with a multimeter
The most reliable way to check the integrity of the electrical part of the engine is to measure the resistance of the windings. To do this, you need to gain access to the contact group of the compressor by removing the protective casing and disconnecting the wires. At the end of the motor you will see three contacts arranged in a triangle. Usually they are marked, but if there is no marking, you need to determine them experimentally.
Take a multimeter and switch it to resistance measurement mode (Ohm). First, check for a breakdown in the housing. Press one probe against any contact, and with the other touch the copper tube or a cleaned area on the compressor housing. The device should show infinity (break). If you see any resistance values, it means that something has happened insulation breakdownand it is dangerous to operate such a compressor - it will “shock” with current and may burn out.
Next we measure the resistance between the contacts. We have three terminals: common (C), starting (S) and working (R). The resistance between the working and common contacts is usually 10-30 Ohms, between the starting and common contacts - 20-50 Ohms, and between the starting and working contacts - the sum of the two previous values (30-80 Ohms). The exact numbers depend on the engine power, but the proportion is important: the resistance of the starting winding is always higher than the working winding.
Approximate resistance values:R (Working) - C (Common): 15 Ohm
S (Starting) - C (Common): 35 Ohm
R (Working) - S (Starting): 50 Ohm
If the multimeter shows a break on any pair of contacts, this means that the winding is burned out. It is impossible to restore it at home. If the resistance is too low (close to zero), this is a sign of an interturn short circuit. In both cases, the compressor needs to be replaced.
How to identify contacts without a diagram?
If there are no markings, find the pair of contacts with the highest resistance - these will be the starting and operating windings. The third, remaining contact is general. The resistance between common and starting will be higher than between common and working.
Checking current consumption and mechanical parts
Electrical measurements are only half the battle. It happens that the windings are intact, the relay is working properly, but the engine still does not start or quickly stalls. In this case, it is necessary to check the current consumption. To do this, current clamps are used, which are placed on one of the power wires when the refrigerator is turned on.
The normal current consumption of a household compressor is from 0.3 to 0.6 Amperes in operating mode. At the moment of start-up, the current may briefly jump to 1-1.5 Amperes. If, when you try to start, the tick needle twitches to 3-5 Amps and the protection immediately triggers, this indicates a jammed mechanism or a difficult start. If the current is close to zero, but there is a hum, there may be an open circuit inside or a faulty relay.
The mechanical part is also checked indirectly. If the compressor is removed, you can try to blow air through the inlet and outlet holes. The air should flow with force, but not be completely blocked. However, the surest sign of a mechanical malfunction is when, when voltage is applied directly (bypassing the relay), the engine hums, vibrates, but the shaft does not rotate.
⚠️ Attention: An attempt to wedge the compressor by applying increased voltage or mechanical impact on the shaft is strictly prohibited. This can lead to rupture of tubes, release of oil and final failure of the unit.
In some cases, replacing the oil helps if it has thickened, but this is a complex procedure that requires evacuation of the system. Most often, with a mechanical wedge, the only solution is to replace the unit. It is also important to check whether the shock absorption system inside the casing is broken - if the springs burst, the compressor will operate with strong noise and knocking.
Table of faults and methods for identifying them
For convenience, we systematize the main symptoms and methods for checking them. This table will help you quickly navigate the situation and understand how likely it is that the compressor is to blame, and not another part of the refrigerator.
| Symptom | Probable cause | Check method | Solution |
|---|---|---|---|
| Click, hum for 5 seconds, silence | Faulty starting relay or jammed compressor | Relay test, starting current measurement | Replacing the relay or compressor |
| The refrigerator is silent, there is no light | No power, the cord or thermostat is burned out | Checking the socket, continuity of the circuit | Repairing the wiring or replacing the thermostat |
| It hums, but does not freeze, warm tubes | Loss of compression, freon leak | Visual inspection of tubes, pressure gauge | Refilling or replacing the compressor |
| Strong knocking and vibration | Destroyed internal suspension | Visual and auditory inspection | Replacement of the compressor |
| Burning smell, blackening of contacts | Interturn short circuit of windings | Measurement of winding resistance | Urgent replacement of the compressor |
As can be seen from the table, the symptoms may be similar, but the reasons are different. For example, the absence of cold when the engine is running more often indicates a freon leak rather than a breakdown of the engine. Therefore, an integrated approach to diagnostics is so important.
Starting the compressor directly: test switching on
There is a way to check the operation of the compressor by applying voltage directly, bypassing the standard relay. This method allows you to understand whether the engine itself is alive if all other elements of the circuit are working. To do this, you will need a piece of wire with a plug and, preferably, a button or circuit breaker for safety.
The connection diagram is simple: phase and neutral are supplied to the common contact and the working contact. The starting contact must be briefly closed with the working or common (depending on the circuit) only at the moment of start. As soon as the engine starts and picks up speed, the starting circuit must be broken. If the compressor runs smoothly, does not heat up and creates pressure, it is working.
☑️ Procedure for direct start
Be careful: With this connection there is no overload protection. If the compressor is seized, the current will increase instantly and the wiring may begin to melt. Keep your finger on the shutdown button and do not keep it turned on for more than 5-7 seconds if startup does not occur.
⚠️ Attention: Direct connection is only possible for diagnostics! You cannot operate the refrigerator without a standard starting relay and protection - this will lead to the windings burning out at the first power surge or overheating.
If after a successful direct start you return the standard relay, and the refrigerator does not turn on again, then the problem is in the relay or control circuit (thermostat, module). If the motor directly hums and stops, it must be disposed of.
When is it necessary to call a technician or replace it?
After all the checks, the condition of the unit becomes clear. If you find a break in the windings, a breakdown in the housing or a mechanical wedge, independent repair is impossible. Replacing a compressor is a complex technological process that requires a vacuum pump, a pressure gauge station, a supply of refrigerant and skills in soldering copper pipes.
An attempt to replace a compressor without pumping out the system and evacuation will result in moisture and air remaining in the pipes. This will cause the formation of an ice plug in the capillary, oxidation of the oil and rapid breakdown of the new engine. In addition, modern refrigerants require precise dosage, and it is impossible to fill the system by eye.
If diagnostics show that the compressor is working, but the refrigerator does not freeze, the problem may be a freon leak or a clogged capillary system. In these cases, the intervention of a specialist with equipment is also required. You can replace only the relay, thermostat or defrost button yourself if you are confident in your abilities.
Is it worth replacing the compressor on an old refrigerator?
If the refrigerator is more than 10-12 years old, replacing the compressor is often not economically feasible. The cost of work and a new unit can be up to 70% of the price of a new refrigerator, and the life of the remaining components (evaporator, condenser) is also coming to an end.
In conclusion, it is worth noting that competent diagnostics can save significant money. A burnt-out relay costing several hundred rubles is often mistaken for a compressor failure. Be careful, use a multimeter and act consistently.
Is it possible to repair a burnt-out compressor?
Theoretically, it is possible to rewind the windings, but in practice this is impractical. Factory sealing is broken; special equipment is required for welding the body, balancing and vacuuming. The cost of such repairs will exceed the price of a new compressor.
Why does the compressor get very hot?
Heating up to 80-90 degrees is normal for a compressor. However, if it is hot to the point that it cannot be touched, or the thermal protection is triggered, this may indicate an interturn short circuit, a lack of freon (the motor is not cooled by the gas flow) or a malfunction of the condenser on the rear grille.
How often do you need to change the compressor?
The service life of a modern compressor is 10-15 years and more. With proper operation (timely defrosting, leveling, cleaning the condenser), it can work for up to 20 years. Frequent replacements are not required.
Is it dangerous to open the compressor yourself?
Yes, it is dangerous. Inside there is compressed gas and oil. If opened incorrectly (for example, with an angle grinder), a spark can ignite oil vapors. Additionally, older models used flammable refrigerants. It’s not worth just sawing the body for the sake of curiosity.
What to do if the compressor hums but does not start?
First check the voltage in the network. If normal, replace the start relay. If it doesn’t help, the piston group is probably jammed. In rare cases, gently tapping the body of a running (on) compressor with a hammer helps, but this is a temporary measure.