Sudden breakdown of the refrigerator always becomes unpleasant a surprise that disrupts the usual rhythm of life. When the equipment stops cooling, and the food inside quickly deteriorates, the first thing many owners think about is calling a technician, but often the reason lies in the electric motor, which you can check yourself. Understanding how to dial a refrigerator compressor will allow you to save time and money, as well as accurately diagnose the need to replace an expensive unit.
The electric motor-compressor is the heart of any refrigeration system, creating the necessary pressure for the circulation of refrigerant. If it fails, the entire cooling cycle stops, and it becomes impossible to restore the cold without replacing the unit. In this article, we will analyze in detail the diagnostic process, the necessary tools and typical resistance values for various models.
Preparation for diagnostics and safety precautions
Before proceeding with direct testing of electrical circuits, it is necessary to ensure complete safety of the work. Any manipulations with electrical equipment should be carried out only when the device is completely disconnected from the AC mains. Unplug the plug from the socket and make sure that there is no voltage on the wires, since the capacitors in the starting circuit can retain charge.
To carry out high-quality diagnostics, you will need a specialized tool, without which accurate measurements are impossible. The main device here is multimeter, which must be in working order and have a charged battery. A set of screwdrivers for removing the protective casing and insulating tape for subsequent assembly will also be useful.
Access to the electrical contacts of the motor is usually hidden under a plastic or metal casing at the lower rear of the unit. Carefully remove the cover, being careful not to damage the fragile plastic latches, and visually inspect the condition of the wires and connectors. The presence of traces of burning, melting of insulation or the characteristic smell of burnt plastic often indicates an interturn short circuit even before measurements begin.
⚠️ Attention: Never touch the metal probes of the multimeter when measuring resistance, as the resistance of your body can distort the readings of the device, especially at high ranges.
It is important to understand that checking the integrity of the windings is only the first stage. Even if the electrical part is intact, mechanical failure of the piston group or jamming of the shaft will require replacement of the unit. However, you should always start by eliminating electrical faults, since this is the most common cause of failures.
Winding diagram and contact search
A single-phase refrigeration compressor motor has three terminals, which are located on a contact strip in the shape of a triangle. These pins correspond to two windings: starting and working, as well as the common wire. Correctly determining the purpose of each contact is critical for correct diagnosis and subsequent connection.
On the contact strip, the pins are often marked with letters or symbols, but over time the markings can be erased or covered with oxides. The standard marking is as follows: C (Common) - common wire, S (Start) - starting winding, R (Run) - working winding. Some European-made models may have the designation M instead of R.
If the visual marking is missing or unreadable, you can determine the purpose of the contacts using a multimeter in resistance measurement mode. The resistance between the common wire and the working winding is always less than that between the common wire and the starting winding. The resistance between the starting and working terminals will be the sum of the two previous values.
Why do the windings have different resistance?
The working winding is made of thicker wire and has more turns, which ensures low resistance and constant operation. The starting winding has a smaller wire cross-section and greater resistance; it is turned on only for a short time to create a starting torque.
For ease of understanding the distribution of resistances, consider their ratio in the table below. This data will help you navigate when taking measurements on a specific unit.
| Pair of contacts | Winding type | Expected resistance (Ohm) | Characteristics |
|---|---|---|---|
| General - Working | Working | 10 - 25 Ohm | Low resistance, thick wire |
| Common - Starting | Starting | 30 - 60 Ohm | High resistance, thin wire |
| Starting - Working | Total | 40 - 85 Ohm | Sum resistance of both windings |
| Any - Housing | Breakdown | Infinity | Dielectric insulation |
Process of testing with a multimeter
After you have reached the contacts and determined their location, you can proceed to direct measurements. Switch the multimeter to resistance (ohms) measurement mode, selecting a limit of 200 ohms or 2 kohms. Touch the probes to any two terminals on the contact strip and record the readings on the device screen.
First, measure the resistance between a pair of contacts that are supposed to be working and common. Record the resulting value. Then move the probes to another pair of contacts, making sure to use the third, remaining pin. Take measurements for all three possible combinations of connecting probes.
☑️ Algorithm for checking the windings
Analyze the obtained numbers. If the device shows specific values in the range from 10 to 80 Ohms, this indicates the integrity of the windings. The absence of readings or a value tending to infinity (one in the most significant digit) indicates an open circuit inside the engine.
Special attention should be paid to checking for insulation breakdown. To do this, switch the multimeter to diode testing mode or to the maximum resistance limit. Press one probe onto any copper fitting on the compressor body (after clearing the contact area of paint), and with the second touch each of the three terminals.
With a working engine, the device should not emit a sound signal, and the arrow or numbers on the display should indicate infinite resistance. The appearance of even the slightest conductivity between the windings and the housing means that a current leak has occurred, which is extremely dangerous for operation.
⚠️ Attention: If you find a breakdown in the housing, further operation of the refrigerator is strictly prohibited, as this creates a direct threat of electric shock when touching the metal parts of the housing.
Interpretation of measurement results
The data obtained require correct interpretation, since the final diagnosis depends on this. A state is considered normal when the sum of the resistances between “General-Working” and “General-Starting” is equal to the resistance between “Starting-Working”. Small deviations within 1-2 Ohms are acceptable due to the error of the device and the temperature of the windings.
If you observe a resistance significantly lower than normal (for example, 1-5 Ohms), this is a sure sign of an interturn short circuit. In this case, the engine may hum, overheat and knock out the automatic fuse in the apartment, but will not be able to start. Repairing such a fault at home is impractical.
The case when the multimeter shows infinity between any pairs of contacts indicates a break. A break can occur either inside the windings due to overheating or in the built-in thermal relay, which is often located inside the motor casing. Sometimes it is enough to let the compressor cool for several hours for the thermal fuse to close again.
It is also worth considering the temperature coefficient of resistance. Cold windings have less resistance than warm windings. Therefore, if you carry out diagnostics immediately after operating the refrigerator, the readings may be slightly higher than the nominal values specified in the technical documentation.
Typical malfunctions and their symptoms
In addition to electrical parameters, there are indirect signs that help make an accurate diagnosis. For example, if the compressor hums but does not start, and the current consumption increases sharply, most likely the piston group is jammed. In this case, the continuity test will show normal winding resistance, but the engine will be useless.
Another common problem is the failure of the starting relay. If the windings are intact, there is no breakdown in the housing, but the motor does not start or starts with a click and immediately stalls, the problem may be in the relay or capacitor. Check the relay for cracks and melting, and also check its contacts.
In some cases, there is a situation where the compressor operates, but does not create the required pressure. This may be due to loss of valve group compression. Electrically, such a unit is fully operational, all resistances are normal, but the refrigeration circuit does not function.
- 🔊 Humming without starting: often indicates a jammed mechanics or a malfunction of the starting relay.
- 🔥 Intense heating: a sign of an interturn short circuit or engine operation in mode overload.
- ⚡ Knocking out plugs: a clear symptom of a short circuit in the windings or a breakdown on the housing.
- 📉 Lack of cold during operation: possible loss of freon or loss of compression, no electrician here than.
Precautions during replacement
If diagnostics showed the need to replace the compressor, it is important to follow a number of rules when dismantling and installing a new unit. Never open the filling fittings of a new compressor ahead of time, since inside there is an inert gas under pressure that protects the system from moisture.
When soldering pipelines, it is necessary to use nitrogen purge or special solders to avoid the formation of oxides inside the system. The entry of even a microscopic amount of moisture or debris into the circuit will lead to rapid failure of the new compressor and blockage of the capillary tube.
⚠️ Attention: Replacement of the compressor and charging with refrigerant should only be done by a certified specialist with the appropriate equipment, since self-charging requires evacuation of the system and accurate dosing of freon.
Also remember that modern refrigerants can be flammable (for example, isobutane), so work should be carried out in a well-ventilated area away from sources of open flame. Compliance with safety precautions when working with gas is as important as when working with electricity.
Frequently asked questions (FAQ)
Is it possible to restore a broken compressor winding?
Theoretically, rewinding is possible, but in practice it is not economically feasible. The cost of work and materials often exceeds the price of a new compressor, and the quality of factory winding cannot be reproduced at home. It is easier and more reliable to replace the entire assembly.
Why does the multimeter show zero Ohm between the contacts?
A reading close to zero indicates a short circuit in the winding turns. This means that the insulation of the wire is destroyed and the current flows along the shortest path, bypassing the resistance of the coil. Such a motor will burn out immediately after being connected to the network.
Does the ambient temperature affect the readings?
Yes, the copper from which the windings are made changes its resistance as the temperature changes. The colder the engine, the less resistance. Therefore, it is better to carry out measurements on a completely cooled unit that has stood without power for several hours.
What to do if the winding resistances are equal?
In some switching circuits, the resistances of the starting and operating windings may be close, but usually there is still a difference. If the resistances are absolutely identical and large, the internal thermal relay may be faulty, breaking the circuit. Let the compressor cool and repeat the test.