A sudden stop of operation of the refrigerator or, conversely, its endless hum often indicates problems with the main heart of the unit - compressor. It is this unit that is responsible for circulating the refrigerant, creating the necessary pressure in the system to maintain low temperatures. When performance drops, products begin to deteriorate and electricity bills rise, even if visually the device looks intact.
Before calling a technician or buying new equipment, it is worth conducting initial diagnostics yourself. This will allow you to understand the scale of the disaster: whether a complex replacement of the unit is required, replacement of the starting relay, or a simple adjustment is sufficient. Modern inverter models old linear motors have their own characteristics, but the basic principles of checking the electrical part and mechanical performance remain similar.
In this article we will analyze the algorithm in detail actions, the necessary tools and the exact values that a working device should show. You will learn to distinguish a burnt winding from a jammed piston and understand when repairs are not economically feasible. Remember that safety is a priority, so all work with electricity is carried out only after a complete disconnection from the network.
Primary visual diagnostics and operation analysis
The first stage is always an external inspection and listening to a working (or trying to start) unit. Do not rush to disassemble the back panel without a basic assessment of the situation. Often signs of a malfunction are visible to the naked eye or audible without the use of tools. Pay attention to the nature of the noise: a steady hum is replaced by a metallic clang, knocking or complete silence.
If the motor hums, but the refrigerator does not freeze, and after a while a click is heard and silence sets in, this is a classic symptom thermal relay or problems with the starting winding. The engine tries to start, but due to high resistance or mechanical jamming, the current increases sharply, and the protection emergency opens the circuit. In such a situation, further attempts to turn on may lead to permanent failure of the unit.
⚠️ Attention: If you smell a burning smell or see melted plastic in the compressor area, immediately stop trying to start. Further diagnostics are possible only after replacing the burnt wiring elements and checking the conductivity of the circuit.
It is also worth inspecting the compressor itself for external damage. The tubes coming from it should not have any traces of oil - this is a sure sign of depressurization of the system. If the oil has leaked, it means that air and moisture have entered the system, which requires not just replacing the motor, but also completely flushing the circuit, replacing the filter-drier and vacuuming.
Necessary tools for accurate diagnostics
For high-quality testing of the performance and integrity of electrical circuits, you will need a minimum set of professional tools. Without them, diagnosis will be only approximate. The main device will be multimeter (tester), capable of measuring resistance in Ohms and current in Amperes. It is desirable to have a dialing function with a sound signal.
To assess the mechanical part and pressure in the system, you will need a pressure gauge station (manifold) and a vacuum pump. However, if your goal is a quick check at home without opening the freon circuit, you can only get by with electrical measuring instruments. To check the outlet pressure, you can use a simple tire pressure gauge connected to the discharge pipe.
- 🔧 Multimeter —to measure the resistance of the windings and check for breakdown.
- 🔧 Pliers and screwdrivers —to dismantle the protective casing and remove the terminals.
- 🔧 Sandpaper —for cleaning contacts before measurements to eliminate errors from oxidation.
- 🔧 Pressure gauge —to check the residual pressure and the ability of the pump to create it.
It is important that the multimeter probes are in good working order and that the battery in the device is not discharged, otherwise the resistance readings may be distorted. Before starting work, make sure your hands are dry and the floor under your feet is non-conductive. All manipulations are carried out exclusively on de-energized equipment.
Checking the electrical part: winding resistance
The most accurate method of primary diagnosis is measuring the resistance of the motor windings. To do this, you need to remove the plastic casing from the back of the compressor and gain access to the contact group. Usually there is a starting and operating relay located there, which must be carefully removed to open access to the three contacts of the motor itself.
The contacts are arranged in a triangle. You need to find the “common” contact (C), as well as the terminals of the starting (S) and working (R) windings. The Atlant refrigerators i Indesit scheme is often standard, but it is better to check the technical documentation of the specific model. Switch the multimeter to resistance measurement mode (limit 2 kOhm) and take measurements between pairs of contacts.
Normal resistance values depend on the motor power, but usually fall within certain ranges. The resistance between the working and common windings should be the smallest, between the starting and common windings - average, and between the working and starting windings - the sum of the two previous values. If the device shows infinity (open) or zero (short circuit), the compressor is faulty.
| Pair of contacts | Normal resistance (Ohm) | Fault symptom |
|---|---|---|
| Working - General | 10 - 30 Ohm | Open or short circuit |
| Starting - General | 20 - 60 Ohm | Open or short circuit |
| Working - Starting | The sum of the two is higher | Insulation failure |
| Case - Any contact | Infinity (∞) | Breakdown to the case |
Pay special attention to checking for breakdown of the housing. One probe is applied to the cleaned area on the compressor housing (where there is no paint or rust), and the second one to the contacts in turn. If the multimeter shows at least some resistance value, it means that the internal insulation is broken. Operate such a unit is deadly.
☑️ Algorithm for checking with a multimeter
Mechanical check: compression test (punchability)
If the electrical part is in order, but the refrigerator does not freeze, the problem may lie in the mechanical part - valves or piston group. The compressor may hum and consume current, but not create the necessary pressure. To check this parameter, you will need to disconnect the capillary tube or use the process pipe, if available.
The essence of the method is to evaluate the blowing force. When a working engine is turned on, a powerful flow of air (or freon) should flow from the discharge pipe, which noticeably blows away dust and creates a characteristic whistle. If the flow is weak, intermittent or absent at all, it means that the valves are worn out or the piston rings are stuck.
⚠️ Attention: When conducting a compression test, there may be residual freon pressure in the system. Be careful not to let the gas jet get into your eyes, as the refrigerant can cause frostbite or chemical burns to your mucous membranes.
A more accurate method is to use a pressure gauge. Connect the pressure gauge station hose to the service connection. When a working compressor starts, the pressure in the system should increase quickly. For household refrigerators, the norm is to reach 6 atmospheres or higher in a short time. If the pressure gauge needle barely creeps or stands still, performance has dropped critically.
Why does the compressor heat up?
Strong heating of the compressor housing (above 90-100 degrees) can be caused not only by overload, but also by a lack of refrigerant in the system. If there is little freon, the motor is not cooled by the returning gas and runs idle, which leads to overheating and eventual combustion.
Diagnostics of the starting and thermal relay
Often the culprit for stopping the refrigerator is not the motor itself, but its “retinue” - the start-protective relay. This small block is responsible for supplying an impulse to the starting winding and protecting against overheating. If the relay is faulty, the compressor will either not start at all, or will operate in short cycles, constantly clicking.
To check the relay, you need to remove it and shake it next to your ear. If a ringing sound is heard inside, it means that the inductor or core is broken, and the part must be replaced. Also check the contacts for carbon deposits. Oxidized contacts create a high contact resistance, which leads to a voltage drop and the inability to start the engine.
The thermal relay is checked by continuity. When cold, the circuit should be closed. If the multimeter shows a break, it means that the bimetallic plastic has worked and has not returned to its original position, or the heating element has burned out. In such cases, replacing the relay solves the problem in 90% of cases, if the compressor itself is intact.
- 🔍 Visual inspection - search for melting, cracks and traces of burning on the relay body.
- 🔍 Checking the coil - it should be intact, without chips and move freely inside.
- 🔍 Testing the contacts —the resistance between the input and output should tend to zero.
Specifics of checking inverter compressors
With the advent of technology No Frost and energy efficiency systems, inverter compressors began to be installed in refrigerators. Their diagnostics are fundamentally different from testing conventional linear models. Such motors do not have a classic starting relay, and they are controlled through an electronic unit (inverter), which converts direct current into alternating current with a variable frequency.
You can check the windings of an inverter compressor with a multimeter, but the results will differ. Their winding resistance is often symmetrical or has very low values, which makes diagnostics difficult without specialized equipment. In addition, even with serviceable windings, the motor may not start due to a failure in the control board.
To accurately diagnose inverters, you need a tester that can measure the starting current and signal shape. At home, you can only verify the integrity of the windings and the absence of a short circuit. If the inverter compressor hums but does not start, or makes intermittent sounds, most often the problem lies in the control module or in the motor itself, which requires complex replacement.
Frequent questions about compressor diagnostics (FAQ)
Is it possible to check the compressor without disassembling the refrigerator?
Completely - no. To access the contact group and tubes, you must remove the back cover and protective casing. However, the primary diagnosis (working/not working, heating/silent) can be made without opening it, relying on the sound and temperature of the capacitor.
What current consumption is considered normal for a household compressor?
For most household models with a power of up to 200 W, the normal operating current is 0.5 - 0.8 Ampere. At the moment of startup, the current may briefly jump to 3-5 Amperes. If the current in operating mode exceeds 1.2 Amperes, this is a sign of overload or interturn short circuit.
Is it worth replacing the compressor on an old refrigerator?
The economic feasibility of replacement depends on the age of the equipment. If the refrigerator is more than 10-12 years old, the cost of a new compressor, the work of a technician and refilling with freon can be 70-80% of the price of a new device. In this case, it is easier to buy new equipment.
Why is the compressor hot, but the refrigerator does not freeze?
This indicates that the motor is working, but is not performing its compression function. Possible reasons: freon leak (the compressor is running empty), blockage of the capillary system or wear of the valve group of the compressor itself. You need to call a technician to find a leak and refill it.