The situation when a refrigerator suddenly stops freezing and its compressor is silent is familiar to many. Often the cause is a failure of the starting relay, which is responsible for starting the engine. In such cases, craftsmen and experienced home craftsmen need to check the performance of the motor itself, eliminating the influence of faulty automation. For this, the method of directly connecting the windings to the electrical network is used.
However, it is worth understanding that such a procedure requires strict adherence to safety precautions. High voltage 220 volts does not forgive mistakes, and careless handling of wires can lead to a short circuit or electric shock. In addition, incorrect connection of the windings can permanently damage the asynchronous motor compressor, turning a simple repair into an expensive replacement of the unit.
In this article we will analyze a step-by-step algorithm of actions that will allow you to safely supply power to the motor. We will look at the differences in circuits for different types of motors, explain how to determine the starting and operating windings with a multimeter, and tell you what to look for when diagnosing. If you are ready to work with electrical appliances, let's start studying the device.
Preparation of the workplace and necessary tools
Before touching the wires, you need to organize a safe space for work. The compressor must be disconnected from the refrigerator and placed on a stable, dry surface. Ideally, on a wooden table or workbench, where moisture is prevented. Make sure that the refrigerator's power cord is unplugged from the outlet and that there are no sources of water in the immediate vicinity.
To carry out diagnostics, you will need a minimum set of tools. The main device will be multimeterwhich will allow you to ring the windings and check the resistance. You will also need pliers, a screwdriver to remove the protective casing, insulating tape and, preferably, a test cord with a plug and terminals. It will not be amiss to have starting capacitorif you plan to check motors with a phase-shifting element.
⚠️ Attention: Never carry out work on connecting the compressor if it is still installed inside the refrigeration chamber or connected to the pipeline system. The motor must be completely dismantled and kept away from flammable substances.
It is also important to check the appearance of the compressor itself. If traces of oil, rust or mechanical damage are visible on the housing, this may indicate depressurization. In this case, it is strictly forbidden to start the engine, since air and moisture could get inside, which will lead to burning of the winding insulation when voltage is applied.
Determining the type of compressor and winding circuit
There are two main types of motors used in domestic refrigerators: with a starting winding (RSIR) and with a starting capacitor (CSIR). Understanding the difference between the two is critical to making a proper connection. In the first case, the starting winding is turned on only at the moment of starting through the starting relay, and in the second - through a capacitor, which can remain in the circuit or be disconnected.
To determine the type of your motor, you need to remove the back cover of the compressor and gain access to the contact group. Usually there are three terminals there, forming a triangle. Two of them are windings, and the third is common wire. In some models, especially old Soviet or specialized ones, there may be four terminals, which indicates the presence of a thermal relay inside the case or a two-speed operating mode.
How to distinguish the starting winding from the working winding without a circuit?
The starting winding (P) always has a higher resistance than the working winding (P). If you measure the resistance between the terminals, the highest value will be between the starting and working terminals, and the smallest - between the working and common terminals.
For accurate diagnostics, use a multimeter in resistance measurement mode (Ohm). Apply the probes to the pairs of contacts and record the readings. The sum of the resistances between pairs of contacts must be equal to the resistance between the remaining two terminals. This will help to calculate which terminal is common and which belong to the windings.
Step-by-step instructions for direct connection to the network
The process of starting an engine without a standard relay requires care. First you need to identify the findings. Usually they are marked with the letters: R (Run - working winding), S (Start - starting winding) and C (Common - common). If there is no marking, we focus on resistance measurements: between R and C the resistance is less, between S and C -more.
To start an RSIR type motor, you need to apply a phase to the common terminal and the working one winding, and briefly short-circuit the starting winding with the working winding or apply an impulse to it. At home, this is often done through a button or simply by briefly touching the wires, but it is safer to use a circuit with a capacitor. Capacitor creates the phase shift necessary for the rotor torque to occur.
☑️ Check before starting
The connection diagram is as follows: one wire from the plug (phase) goes to the common contact of the compressor. The second wire (zero) is connected to the working winding. The starting winding is connected to the working winding through a starting capacitor or is closed manually only at the time of start. As soon as the engine picks up speed, the starting winding circuit must be broken, otherwise it will burn out.
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| Winding type | Designation | Resistance (Ohm) | Function |
|---|---|---|---|
| Working | R (Run) | Low (10-30 Ohms) | Main engine operation |
| Starting | S (Start) | High (30-60 Ohm) | Rotor start |
| General | C (Common) | Sum of R and S | Network connection |
| Grounding | GND | Protection from breakdown |
Diagnostics of faults during startup
If, when power is applied, the engine hums but does not start, this may indicate a jammed piston group or lack of starting torque. In the first case, when the rotor is physically unable to turn due to wear and tear on the mechanical parts, a characteristic low-frequency hum is heard. Attempts to start such a compressor “with a jerk” can help only temporarily, but most often the unit requires replacement.
Another reason is an insulation breakdown or an interturn short circuit. If the multimeter shows a resistance close to zero or, conversely, an open circuit (infinity), then the winding has burned out. It is also worth checking the resistance between the terminals and the copper housing of the compressor. If the device shows at least some value, it means there is ground fault, and operating such a motor is dangerous to life.
⚠️ Attention: If the compressor makes a loud metallic knock or vibration when starting, immediately turn off the power. This is a sign of serious mechanical damage to the internal components; further work will lead to rupture of the housing.
Sometimes the engine starts, runs for a few seconds and turns off. This may be due to overheating or internal thermal protection tripping, if it survives. The cause may also be insufficient voltage in the network or too much load on the shaft. Check whether the shaft rotates freely (if there is access) and whether there is air leakage through cracks in the pipes.
Use of a starting capacitor
For reliable starting of many models of refrigeration compressors, especially more powerful ones or those designed to work with refrigerants such as R600a i R134a, a starting capacitor is required. Its capacitance usually varies from 10 to 50 µF depending on the motor power. Using a capacitor of the wrong size may result in overheating of the windings or failure to start.
The capacitor is connected in series to the starting winding circuit. At the moment of switching on, it creates the necessary phase shift of the current, simulating two-phase power. After accelerating the rotor, it is advisable to disconnect the capacitor, although in many household circuits it remains connected permanently (it works as a phase shifter). To check the performance of the motor outside the refrigerator, a short-term switching on is enough.
It is important to use capacitors designed for a voltage of at least 400-450 volts. Conventional electrolytic capacitors are not suitable for such purposes, as they can explode when operating in an alternating current circuit. Look for the marking AC or ~ on the body of the part.
Safety measures and final recommendations
Starting the compressor directly is an emergency measure for diagnostics, and not a method of permanent operation. Operating without relays and thermal protection leaves the motor vulnerable: if overloaded or jammed, it will burn out in a matter of minutes. Therefore, if the check shows that the motor is in good condition, it is necessary to install a new starting relay corresponding to the refrigerator model as soon as possible.
Do not forget that when the compressor is operating, air under pressure may escape from its nozzles. If there is any refrigerant left in the system, it will come out along with the oil. You need to work in a well-ventilated area, away from open flames, since oil vapors and some types of freons can be flammable or toxic at high concentrations.
If you are not confident in your knowledge of electrical engineering or you do not have the necessary tools, it is better to contact a professional technician. Repairing refrigeration equipment is fraught with risks, and economical