A sudden stop in the operation of the refrigerator often throws owners into a stupor, especially when the unit stops cooling, and the ice inside is already beginning to melt. Self-diagnosis in such a situation allows you to save time and money by calling a specialist only for complex repairs or replacement of components. The first suspect is usually the starting relay, but if it is excluded from the circuit, you can get direct access to the very heart of the system - the compressor.
Checking the motor bypassing the standard automation requires caution and an understanding of the principles of operation of the electrical circuit. Single-phase asynchronous motorsused in household appliances have a specific winding design that must be taken into account when testing. Our goal is to determine whether the motor itself is alive, or whether the problem lies deeper in the freon circulation system.
Before taking up tools, you need to understand the risks. Working with high voltage 220 volts requires strict adherence to safety precautions. Never touch exposed wires and terminals while applying voltage to the compressor. In addition, if the motor is under pressure or has visible mechanical damage to the housing, starting it can be dangerous.
Operation principle and structure of the electric motor
To effectively check the unit, you need to understand how it works. Inside the sealed casing there is an electric motor, the shaft of which drives the compressor pistons. The electrical part consists of two main stator windings: working and starting. The working winding has a larger wire cross-section and lower resistance; it is responsible for the main rotation of the rotor.
The starting winding is made of thinner wire and has a high resistance. Its task is to create an initial torque, after which it must be turned off. In normal mode, the starting relay is responsible for this, but during direct testing we simulate its operation manually or using a push-button mechanism. Interturn short circuit or a break in any of the windings makes starting impossible.
It is also important to take into account the presence of a capacitor in some models of refrigerators. In circuits with capacitor starting capacitance helps create a phase shift to start the rotor. If your model has a starting capacitor, its serviceability also affects the ability to start the motor without a standard relay. The absence of a spark or a hum without rotation often indicates problems with the starting circuit.
⚠️ Attention: The sealed compressor casing cannot be opened to diagnose the windings. All measurements are carried out only through the external contact group (three terminals). Violation of the tightness will lead to moisture and oxygen getting inside, which will instantly disable the unit.
Necessary tools and preparation for work
To carry out high-quality diagnostics, you will need a minimum set of tools that most home craftsmen can find. The key device will be multimeter (tester), capable of measuring resistance in Ohms and current in Amperes. Without it, the check will be only approximate and may not give an accurate answer about the condition of the windings.
In addition to the measuring device, you will need screwdrivers to remove the protective casing at the back of the refrigerator, pliers and insulating materials. To safely start the motor bypassing the relay, they often use a special circuit with a button or simply carefully manipulate the wires, which requires special concentration. It would also be a good idea to prepare current clampsif you plan to measure the starting current.
- 🛠️ A multimeter with a continuity function and measuring resistance up to 2 kOhm.
- 🔌 Wires with clamps “crocodile” for temporary connection.
- 🧤 Dielectric gloves and tools with insulated handles.
- 💡 Incandescent lamp or powerful resistor for test load (optional).
Before starting any work, the refrigerator must be completely disconnected from the power supply. Unplug from the socket and let the unit stand for 10-15 minutes. This is necessary so that the residual voltage in the circuits dissipates and the refrigerant in the system comes into equilibrium, which will reduce the pressure in the circuit.
☑️ Preparation for diagnostics
Visual inspection and removal of the relay
The first stage of diagnosis is a careful visual inspection. When you remove the back panel of the refrigerator, you will see a compressor with a plastic or metal box attached to the bottom or side. This is the start relay. It is this that we have to temporarily exclude from the circuit.
Carefully remove the compressor casing. It is usually held in place by latches or screws. Inside you will see a contact group with three terminals and a relay connected to them. Before disconnecting the wires, it is strongly recommended to take a photo of the connection diagram or sketch it. The colors of the wires from different manufacturers (Indesit, Bosch, Samsung) may differ, and an assembly error will lead to a short circuit.
Remove the relay from the compressor contacts. It can be fixed with a metal bracket or simply sit tightly on the terminals. Inspect the relay itself: if you hear a rattling sound inside, see carbon deposits, melt the plastic, or smell a burning smell, then with a high degree of probability the problem was in it. However, our task is to check the motor, so we put the relay aside.
Inspect the contact pad on the compressor itself. The three pins forming a triangle must be clean, free of oxides and signs of corrosion. If the contacts are dirty, they can be carefully cleaned with fine sandpaper or alcohol, but this must be done extremely carefully so as not to damage the insulation of the terminals inside the casing.
Testing the windings with a multimeter
The most reliable method of initial testing is measuring the resistance of the windings. On the contact group, the conclusions are usually marked: C (Common) - common, R (Run) - working winding, S (Start) - starting winding. If there are no markings, you need to calculate them empirically by measuring the resistance between each pair of contacts.
Switch the multimeter to the resistance measurement mode (Ohm). Measure the resistance between all three pairs of contacts. Between the common and working windings, the resistance should be minimal (for example, 10-20 Ohms). Between general and starting - average (30-50 Ohms). The sum of these two values should give the resistance between the working and starting windings (the highest value, for example, 40-70 Ohms).
If the device shows one (infinity) on any of the pairs, it means in the circuit Open circuit. If the resistance is close to zero, a short circuit has occurred. In both cases, the compressor is faulty and requires replacement. It is also important to check the breakdown on the housing: one probe is placed on any contact, the second - on the metal body of the compressor, which has been stripped of paint. The device should show infinity.
| Pair of contacts | Normal resistance | Possible malfunction | Actions |
|---|---|---|---|
| General - Working | 10 - 25 Ohm | Infinity / 0 Ohm | Replacement of the compressor |
| General - Starting | 30 - 55 Ohm | Infinity / 0 Ohm | Replacing the compressor |
| Working - Starting | The sum of the two is higher | Inconsistency with the sum | Checking contacts |
| Any - Housing | Infinity (∞) | Any value | Insulation breakdown, dangerous! |
Why resistance are they different?
The starting winding is wound with thinner wire and has more turns to create high active resistance and phase shift. The working winding is made of thick wire to minimize energy losses during constant operation.
Direct start of the compressor (Test start)
If the continuity test shows normal values, we proceed to the most important stage - trying to start. To do this, we need to apply 220 volts directly to the working winding and briefly to the starting winding. In a professional environment, a special starting device is used for this, but at home you can use a circuit with a button.
Connect two wires from the plug to the contacts C (common) and R (working). The third wire (phase) through the button (or just a short touch) must be applied to the contact S (starter). When connected to the network, a buzzing sound is heard. If at the same moment voltage is briefly applied to the starting winding, the rotor should jump off.
Successful starting is characterized by a smooth, monotonous hum of the running motor. If the compressor has started, it should work steadily, without overheating in the first minutes. If a crackling sound is heard, a buzzing turns into a quiet hum or the circuit breaker knocks out, it means there is a mechanical inside the piston group or an interturn short circuit that the tester did not detect. Wedge wedge piston group or interturn short circuit, which was not detected by the tester.
⚠️ Attention: When connected directly, the compressor has no protection against overheating and restarts. Do not keep it turned on for more than 3-5 minutes in test mode. Long-term operation without a standard relay and thermal protection can lead to burnout of the windings.
Analysis of results and search for hidden defects
After the tests, it is necessary to analyze the data obtained. If the motor starts and runs, but the refrigerator does not freeze, the problem may not be electrical, but mechanical or a freon leak. The compressor may create pressure, but not enough for the cooling cycle, or the circulation of the refrigerant is impaired by a blockage in the capillary pipe.
There is also the concept of “turn-to-turn short circuit,” which is difficult to identify with a conventional multimeter. In this case, the resistance of the windings may be normal, but when voltage is applied, the current consumption will be significantly higher than the rated values. For accurate diagnosis in such cases, it is necessary to measure the current consumption current clamps at the time of operation.
If the compressor hums, but does not start even when a pulse is applied to the starting winding, there is a high probability of jamming. In some cases (not always), the so-called “voltage increase method” or shock loading helps, but these methods are risky and require special equipment. Most often, a jammed compressor must be replaced.
- 🔊 A steady hum and vibration are a sign of a working mechanical part.
- 🔥 Rapid heating of the housing (in 1-2 minutes) is a sign of an interturn short circuit.
- 🔨 A metallic clang or knock is a mechanical destruction of the components inside the casing.
Frequent errors during self-diagnosis
Beginners often make mistakes that can lead to false conclusions or damage to working equipment. One of the most common is confusion in contacts. An attempt to apply operating voltage only to the starting winding or an incorrect connection of the terminals can instantly burn the winding.
Another mistake is ignoring the condition of the wires. Old insulation may crack, causing a short circuit when trying to start the motor. Always check the integrity of the insulation on suitable cables. Also, do not forget that some modern inverter compressors (Linear Inverter) cannot be checked using the method described above, since they are controlled by a complex electronic unit rather than a simple relay.
An unreasonably long test run is another risk. Remember: if the engine does not start after 2-3 attempts, further experiments are useless and dangerous. The problem is either mechanical or electrical in the windings, and this cannot be solved by “overclocking.”
Questions and answers (FAQ)
Is it possible to leave the refrigerator operating without a start relay?
No, operating a refrigerator without a start relay is impossible and dangerous. The relay provides the necessary phase shift for starting and, more importantly, turns off the starting winding after gaining speed. Without a relay, the starting winding will burn out in a few seconds, since it is not designed for long-term operation.
Why does the compressor hum, but does not start, although the resistance is normal?
This is a classic sign of a mechanical wedge of the piston group or lack of compression. Also, the reason may be dried up oil, which prevents the pistons from moving, or a malfunction of the starting capacitor, if it is provided for in the design.
Is it safe to check the compressor from a car battery?
No, the compressors of household refrigerators operate on a 220V AC network. The motor will not start from a 12V DC car battery, since it will not have enough voltage and torque, and the engine design is not designed for this.
How to distinguish an inverter compressor from a conventional one?
Inverter models usually have an electronic control board attached directly to the motor housing and are quieter. It is impossible to check them by testing the windings and direct starting from a 220V network - they are controlled by complex electronics with frequency conversion.
What to do if, when testing, the multimeter shows "1" (infinity)?
This means an open circuit. It is possible that the thermal protection inside the casing has burned out (it is connected in series to the circuit) or the winding wire has broken. In 95% of cases, such a compressor must be disposed of and replaced, since repairs inside the containment zone are impossible.