When the refrigerator stops cooling or makes unusual sounds, the first thing that comes to mind is to check its “heart,” that is, the compressor. For many users, the internal structure of household appliances remains a mystery, hidden behind a metal casing at the bottom of the case. Understanding exactly what this unit looks like and what elements surround it will help you carry out an initial diagnosis yourself or correctly explain the problem to a technician.
Visually, the motor-compressor is a massive black or gray metal cylinder, hermetically sealed on all sides. It is attached to a frame at the bottom of the unit and is surrounded by a system of pipes, filters and electrical components. In this article we will analyze in detail the appearance of a standard compressor, its key elements and signs by which you can determine its condition without opening the case.
Exterior view of the compressor: main body and fastening
If you look into the niche at the bottom of the refrigerator, removing the protective panel or back cover, you will see the main element of the system - hermetic compressor. Most often it is painted matte black, although there are models in silver or dark gray. The body shape is usually cylindrical or slightly flattened spherical, resembling a large barrel lying on its side. Such a unit weighs impressively, from 10 to 20 kilograms, which immediately catches your eye when you try to move it.
The motor housing has no visible bolts or screws, since it is welded or brazed from two halves to ensure complete tightness. On the surface of the metal you can often find factory stickers with technical information: model, refrigerant, power and production date. This data is critical when selecting a replacement. The unit is attached to the metal frame of the refrigerator through special shock-absorbing bushings that dampen vibration. If you see that the motor is “hanging” on the tubes or the rubber feet are dry and cracked, this requires immediate intervention.
It is important to note that the surface of the housing is always hot in working condition. This is normal and indicates refrigerant compression. However, if the metal is hot to such an extent that it is impossible to touch it, or, conversely, it is icy when the engine is running, this is a signal of a serious malfunction of the system.
Pipelines and connections: where do the copper lines go?
Copper tubes extend from the top of the black “barrel”, which are the arteries of the refrigeration system. Visually, two main types of connections can be distinguished. The first group is discharge tubes, they are usually thinner and lead to the condenser (the grill at the back of the refrigerator). The second group is suction tubeswhich often have a larger diameter and can be covered with a layer of thermal insulation (white or gray soft material) to prevent the formation of condensation.
Copper oxidizes over time, acquiring a dark, almost brown tint, but in solder areas it can remain light if there has been recent intervention. Pay attention to the joints of the tubes with the compressor housing. There should be no traces of oil, black burning or frost. The presence of oily stains around the fittings is a sure sign of depressurization of the system, which in 90% of cases requires replacing the compressor and refilling with freon.
⚠️ Attention: Never try to bend or flare copper tubes with your own hands without special tools and skills. Copper is extremely fragile after long use, and one awkward movement will lead to a fracture of the line and leakage of the entire refrigerant.
In some models of modern refrigerators with the No Frost system, you can see a plastic casing hiding part of the tubes, but the main terminals of the compressor always remain metal and are accessible for visual inspection.
Start-protective relay and thermostat
A small plastic block is usually attached to the side or back of the compressor, where the electrical contacts exit. This starting relay. It can be black, white or gray, rectangular or cylindrical. It is this component that provides the initial impulse to start the motor and protects it from overcurrent. The relay is often marked with arrows indicating the correct installation position (for example, “UP” or “TOP”).
Next to the relay, sometimes in a single housing, and sometimes separately, is located thermal protection relay. Visually, this is a small part with a bimetallic plate inside. If the motor overheats, this part opens the circuit, stopping the operation of the unit. When inspecting, pay attention to the color of the plastic: if the relay has turned black or melted, it means that critical overloads have occurred in the system, and the unit itself has most likely failed.
How to test the relay by ear?
Take a working relay and shake it next to ear. If a ringing sound is heard inside, it means the contacts are normal (in some types of relays). A dull sound may indicate destruction of the internals, but this is not always an accurate diagnostic method without a multimeter.
The electrical wires going to the relay must be intact, without melted insulation. Often the cause of equipment failure is the oxidation of the contacts at the junction of the wires with the compressor terminals, and not a breakdown of the motor itself.
Table: Visual signs of the condition of the compressor
For ease of diagnosis, we have compiled a summary table that will help classify the condition of the motor by external signs. Remember that a visual inspection is only the first stage, which should be followed by an instrumental check.
| External sign | Probable cause | Required actions |
|---|---|---|
| The body is covered with an oily film | Depressurization of the system, leakage of freon | Call a technician to find the leak and refill |
| Strong vibration, rumble at start | Wear of shock absorbers or breakage of the internal suspension | Replacement of rubber bushings or compressor |
| Melted plastic relay block | Short circuit or overcurrent | Replacing the starting relay and checking the windings |
| The tubes are covered with a thick layer of frost | Malfunction of the thermostat or lack of freon | Diagnostics of the defrost and pressure system |
| Rust on the lower part of the body | High humidity, water ingress during washing | Cleaning and treatment with the converter rust |
It is worth considering that some visual defects may be cosmetic and not affect operation, but it is not recommended to ignore them, as they can become harbingers of more serious problems.
Sound diagnostics: what does engine noise indicate
Although the topic of our article is visual inspection, sound is an integral part of the “image” of a running motor. A working compressor produces a uniform, low-frequency hum. This sound may become louder when turning on and off, which is normal. However, there are anomalies that cannot be ignored.
If you hear a metallic clanging, knocking or squeaking sound, this indicates mechanical destruction of the internal components: piston group, valves or bearings. In such cases, the motor may appear intact on the outside, but is functionally dead. Also an alarming signal is a situation when the motor hums for 1-2 seconds, clicks and goes silent. This is a classic symptom compressor wedge or malfunction of the start relay.
- 🔊 Uniform humming - normal operating mode.
- 🔨 Metal knocking - destruction of the mechanical parts.
- ⚡ Clicks and silence - a problem with starting or electrical.
- 🌪️ Whistling or hissing - a gas leak or a circulation problem.
In modern inverter models, the sound of operation can be almost inaudible, since the motor does not turn off completely, but only changes momentum. Therefore, the absence of characteristic shutdown clicks in such models is the norm, and not a breakdown.
Types of compressors: differences in appearance
Not all motors look the same. In modern refrigerators you can find several types of designs, and knowledge of their features will help you not to get confused when you see a “non-standard” unit.
The most common type is piston compressor. It looks like the one described above: a heavy cylinder. However, there are rotary compressorswhich often have a more compact, sometimes vertical, body. They are found less frequently, mainly in built-in appliances or refrigerators of small dimensions.
It is worth mentioning separately inverter motors. Visually, they may differ in the presence of an additional electronic control unit, integrated directly into the housing or located nearby in the form of a separate “washer”. Such engines are mounted differently, often without traditional spring suspensions, since they operate smoothly and do not require strong vibration isolation. Their body can be made of lighter alloys and have a different shape, resembling a pear or a cone.
⚠️ Attention: Do not try to change a conventional compressor to an inverter one (and vice versa) without completely reworking the electrical circuit of the refrigerator. They have fundamentally different control and power requirements.
When replacement is required: critical signs
Visual inspection often gives the answer to the question of whether it is worth repairing the equipment or is it easier to buy a new one. If you find that the compressor housing has through-hole damage, traces of deep corrosion with holes, or obvious signs of fire (melting of paint to metal), repair is not economically feasible.
Replacement is also necessary if, when you try to start, the motor makes a loud bang and knocks out automatic fuses in the apartment. This indicates an interturn short circuit of the windings. Visually, this can be seen by the blackening of the place where the wires exit the housing or the specific smell of burnt insulation coming from the bottom of the refrigerator.
☑️ Signs of the need for replacement
Independent replacement “at random” without pressure gauge station will lead to the fact that the refrigerator will work for several hours or days, after which the new motor will fail.
FAQ: Frequently asked questions
Is it possible to paint a compressor if it is rusty?
You can only paint the outer surface of a pre-cleaned and degreased casing of a special heat-resistant paint for metal. It is strictly forbidden to paint over copper tubes, soldering points and electrical contacts. Paint on the tubes will hide future leaks and make diagnostics difficult.
Why is the compressor hot, but the refrigerator does not freeze?
This indicates that the motor is running, but there is no refrigerant circulation. Possible causes: clogged capillary tube, freon leak, or broken valves inside the compressor itself. Diagnostics of the pressure in the system is required.
How much does a standard compressor weigh?
The weight of a household compressor for a refrigerator with a volume of 250-350 liters is usually from 10 to 12 kg. More powerful models for large Side-by-Side refrigerators can weigh up to 18-20 kg.
Is it possible to restore a hermetic compressor?
In domestic conditions - no. Factory welding of the housing cannot be restored with a guarantee of tightness. In the event of an internal breakdown, the unit must only be completely replaced.