When faced with the fact that the refrigerator has stopped freezing, many owners immediately panic, anticipating expensive repairs or the purchase of new equipment. However, before calling a specialist, it is worth carrying out an initial diagnosis to understand what the cause of the breakdown is. Most often, the problem lies precisely in compressor, which is the heart of the entire cooling system.
The compressor is a motor-pump responsible for circulating the refrigerant through the pipes. If it doesn't work, no cold is generated and the food starts to spoil. In this article, we will take a closer look at how to determine the health of the engine, what tools you will need, and when DIY repairs can be dangerous.
Understanding the principles of operation will allow you to save time and money by avoiding unnecessary calls to specialists for simple tasks. However, it is worth remembering that working with electrical equipment requires strict adherence to safety precautions.
If you notice that the chamber is warm and the engine is silent or, conversely, hums without stopping, this is the first signal to action. Diagnostics begins with careful observation of the behavior of the unit.
Primary visual diagnostics and sound analysis
The first thing to do when a malfunction is detected is to listen to the operation of the unit. A working refrigerator emits a smooth, barely noticeable hum when the compressor is running. If you do not hear any sounds, or, on the contrary, you hear clicks, a hum that turns into silence, or a strange metallic clanging, these are clear signs of a problem.
Go to the back of the device. Carefully touch the compressor housing with the back of your hand (so as not to get burned if the motor is hot). It should be warm, but not hot to the point where it is impossible to hold your hand. Excessive heating or, conversely, an icy case indicates a malfunction in the system.
Pay attention to the behavior start relay. If you hear a characteristic click, followed by an attempt to start the engine, and then another click and silence, most likely the protection has tripped. This may indicate an interturn short circuit or jamming of the piston group.
⚠️ Attention: If you smell burning or see sparking in the area of the electrical connectors, immediately unplug the refrigerator. Further operation may lead to a fire.
Visual inspection also includes checking the integrity of the tubes and the absence of oily smudges on the motor housing. Oil can leak through the seals due to severe wear or overheating, which is a critical sign.
Checking the electrical circuit and starting relay
Before sinning on the motor itself, it is necessary to rule out a malfunction of the starting relay and thermostat. It is these elements that most often fail, simulating engine failure. To carry out the work you will need a multimeter.
Remove the protective casing from the compressor and carefully disconnect the relay. Visually inspect it for melting, blackening or cracks. If the relay body is damaged, replacing it can solve the problem without interfering with the engine itself.
Using a multimeter in continuity mode, check the relay contacts. In normal condition, they should ring or not ring depending on the type of relay (electromagnetic or posistor). For an accurate check, it is best to find a similar working relay or use special resistance tables for your model.
How to check a posistor relay?
A posistor relay contains a ceramic element that is heated by current and opens the circuit. Check its resistance: when cold it should be low (several ohms), and when heated it should increase sharply. If the resistance in the cold is infinite or zero, the relay is faulty.
Also check the thermostat. Connect its contacts directly. If after this the compressor starts, then the problem was in the temperature sensor, and not in the motor.
- 🔌 Disconnect the refrigerator from the electrical outlet before removing any parts.
- 📸 Take a photo of the wiring diagram before disassembling so as not to mix up the contacts during assembly.
- 🧹 Clean the contacts from oxides and dust before checking.
If the relay and thermostat are working properly, but the engine still does not start, we move on to a deeper diagnosis of the windings.
Diagnostics of the compressor windings with a multimeter
This is the most reliable way to check Electrical integrity the engine. You will need access to three contacts on the compressor housing (usually arranged in a triangle). Remove the relay and starting capacitor to free the contacts.
Switch the multimeter to resistance measurement mode (Ohms). Measure the resistance between pairs of contacts. For a working single-phase motor, you should get three values: the resistance between the starting and working windings, between the starting and common windings, and also between the working and common ones.
The sum of the two smaller resistances should be equal to the largest (resistance between the starting and working windings). If the device shows infinity (open) or zero (short circuit), the motor is faulty.
It is also necessary to check the breakdown on the case. Apply one multimeter probe to any contact, and the second to a copper tube or unpainted part of the case. The device should show infinity. Any resistance value indicates an insulation breakdown, which makes operation dangerous.
The table below shows approximate resistance values for different types of windings, however, the exact data depends on the model compressor.
| Measurement type | Normal value | Symptom of malfunction |
|---|---|---|
| Working winding | 10-20 Ohm | Open or short circuit |
| Starting winding | 20-40 Ohm | Open or short circuit |
| Breakdown to housing | Infinity (∞) | Any numerical value |
| Thermal protection | 0 Ohm (closed) | Infinity (open) |
If the measurements show deviations from the norm, the compressor will most likely need to be replaced. Repairing windings at home is practically impossible and economically unfeasible.
Checking pressure and mechanical parts
Electrical service does not guarantee that the compressor will be able to create the required pressure. Mechanical failure of the valves or piston group leads to the fact that the engine hums, but does not pump freon. To check, you will need a pressure gauge station.
Connect the pressure gauge to the service fitting (if any) or cut into the system. When starting up, a working compressor should quickly build up pressure. For R134a this is about 6-8 atmospheres on the discharge side. If the pressure gauge needle barely creeps or stands still, the compressor “does not hold” pressure.
⚠️ Attention: Working with refrigerants requires a license and special equipment. Independent release of freon into the atmosphere is prohibited by law in many countries.
There is a popular, but crude, “finger” test method. With the compressor running, place your finger on the discharge port. You should feel strong pulsation and air pressure. If the air just gets warmer without pressure, it means the valves are worn out.
Another sign of a mechanical malfunction is a metallic knock inside the case during operation. This may mean that the bearings have broken or the connecting rod has broken. In this case, it is better to turn off the engine, as it may completely collapse, clogging the system with chips.
Symptoms of interturn short circuit
A special case that is difficult to diagnose with a multimeter is turn-to-turn short circuit. It occurs when the insulation between the turns of the winding is broken. In this case, the resistance may change slightly, and the tester will show “normal”, but the engine will not work.
The main symptom is the knocking out of the circuit breaker (plugs) in the apartment when the refrigerator is turned on. Also, the winding can heat up very quickly and unevenly, emitting a specific smell of burnt insulation.
To accurately diagnose interturn short circuits, professionals use current clamps. They measure the current drawn by the motor during startup and operation. If the current significantly exceeds the rated current indicated on the nameplate (for example, instead of 1A, 3-4A is consumed), it means that there is a short circuit in the winding.
At home, without current clamps, you can only rely on indirect signs: overheating, odor and network protection. If the refrigerator is new and immediately “knocks out the light,” this is an almost guaranteed interturn short circuit.
Replacement or repair: which is more profitable?
If diagnostics showed a malfunction of the engine itself, the owner is faced with the question: repair or replace? In 95% of cases compressor replacement is the only correct decision. Modern hermetic compressors are not intended for disassembly and repair.
The cost of a new motor, work to replace it, evacuation of the system and refilling with freon can be up to 70% of the price of a new refrigerator. However, if the refrigerator itself is of high quality and expensive, replacement makes sense.
When replacing the engine, it is also necessary to replace the filter drier, since the old one could accumulate moisture and oil breakdown products. Ignoring this stage will lead to repeated breakdown in a short time.
☑️ Action plan in case of breakdown
Repairing old Soviet refrigerators is sometimes possible by rewinding the engine, but finding a technician and parts is now extremely difficult. For modern technology Atlatnt, Indesit, Bosch or LG only the method of replacing the complete unit is used.
Frequently asked questions and answers (FAQ)
Is it possible to start the compressor directly without a relay?
Theoretically, it is possible by applying voltage directly to the working and starting windings, but doing this is extremely dangerous without skills. You can burn the windings or get an electric shock. This method is used by craftsmen only for a short-term check of the performance of the motor outside the refrigerator.
Why is the compressor hot, but the refrigerator does not freeze?
This indicates that the motor is working, but is not performing its function. Possible causes: freon leak, clogged capillary tube or wear on the valves of the compressor itself. The system needs to be diagnosed by a specialist.
How long does a compressor last on average?
The service life of a modern compressor is from 10 to 15 years. However, with frequent voltage fluctuations, overheating or improper operation (for example, installation close to the wall), it can fail much earlier.
Can a compressor from a refrigerator be used for other purposes?
Yes, old serviceable compressors are often used to create homemade spray guns, airbrushes, or for inflating tires. They are capable of creating high pressure, but have low air capacity.