The situation when the refrigerator stops freezing, and the compressor either hums but does not start or is silent, is familiar to many owners of household appliances. Often the cause is a malfunction of the start relay or a breakdown in the electrical circuit in the motor itself. Before buying expensive spare parts or calling a technician, it is important to carry out initial diagnostics to understand whether you are alive unit or the problem lies in the control electronics.
Determining the winding terminals is a basic skill necessary for replacing the start-up relay, installing a compressor from another refrigerator or connecting the engine to the network for testing. Incorrect connection of the wires can lead to instantaneous burnout of the winding or jamming of the piston group, so the process must be approached with full responsibility and understanding of physical processes.
In this article we will analyze methods for identifying contacts, working with a multimeter and the features of various types of compressors. You will learn to distinguish the starting winding from the working winding by resistance and understand why the color of the wires is not always a reliable guide in repairs.
Basic principles of operation and types of windings
The refrigerator compressor is an electric motor operating from a single-phase network. To create a rotating magnetic field and start the rotor, two main ones are used: working (main) and starting (auxiliary). The working winding occupies most of the stator slots and has a thicker wire, which ensures a constant magnetic field during operation. stator windings: working (main) and starting (auxiliary). The working winding occupies most of the stator slots and has a thicker wire, which ensures a constant magnetic field during operation.
The starting winding is made of a wire of a smaller cross-section and has a larger number of turns. It comes into operation only at the moment the engine starts for a few seconds, creating the necessary phase shift. After the rotor accelerates, the starting winding is turned off using a starting relay or a centrifugal switch. In some modern models inverter compressors the principle of operation may differ, but classic circuits remain the standard for most household refrigerators.
⚠️ Attention: An attempt to apply voltage directly to the starting winding without a working one will lead to rapid overheating and an interturn short circuit. Always check the connection diagram before applying power.
Necessary tools and safety measures
To carry out diagnostics, you will need a minimum set of tools that every home craftsman should have. The main device will be multimeter (tester), capable of measuring resistance in the range from 0 to 200 Ohms. It is advisable to use a device with a dialing function, since a sound signal speeds up the search for contacts.
You will also need screwdrivers to remove the protective casing, pliers and, possibly, insulating tape or casings for marking the wires. Before starting any work, you must completely turn off the power to the refrigerator by removing the plug from the socket. Even after turning off the power, the capacitors may retain a charge, so do not touch live parts with bare hands.
Pay special attention to the condition of the wire insulation. If you see melted plastic, blackening or cracks, restoring such a unit is pointless and dangerous. An opened compressor with a broken housing seal also cannot be repaired at home.
☑️ Checking readiness for diagnostics
Visual inspection and marking of leads
The first stage of diagnosis is visual analysis. After removing the start protection relay, you will see three contact pins arranged in a triangle on the compressor housing. On many modern units, such as Atlant or Indesit, letter markings can be applied next to the terminals, although over time the paint often wears off.
The standard marking looks like this: the letter R (Run) indicates the operating winding, S (Start) - starting, and C (Common) - common wire. Sometimes there are notations in German or French style, where the common point can be designated as 1 or N. If the markings are missing or unreadable, you will have to rely only on measurements.
Pay attention to the color of the wires running from the relay to the contacts. Although manufacturers try to adhere to standards, there are no guarantees. Typically, a black or blue wire leads to the working winding, a red or white wire to the starting winding, and a yellow-green or brown wire to the common point. However, relying only on color is dangerous, since during previous repairs the wires could have been mixed up.
Why may there be no markings?
On many old Soviet refrigerators and budget Chinese models, there are no markings on the body at all. Craftsmen have to determine the conclusions exclusively by measuring the resistance, since the color coding in different batches may differ.
Methodology for identifying windings with a multimeter
The most reliable method of identification is measuring the active resistance between pairs of contacts. Switch the multimeter to resistance measurement mode (200 ohm limit). You need to make three measurements between three contacts, conventionally calling them 1, 2 and 3. Write down the obtained values.
The calculation logic is based on the physics of the engine: the greatest resistance will be between the ends of the starting and working windings (since they are connected in series). The working winding will have the lowest resistance, and the average value will indicate the starting winding. The common wire is always located between the point of least and average resistance.
For clarity, consider an example. Let's say we get the following values: between contacts A-B - 30 Ohms, between B-C - 15 Ohms, between A-C - 45 Ohms. The largest value (45 Ohms) is the sum of the resistances of both windings. Therefore, the contact that is not involved in this measurement (in this case B) is Common. The remaining two contacts are the ends of the windings.
| Pair of contacts | Resistance (Ohm) | Output |
|---|---|---|
| Pin 1 - 2 | 45 | Sum of windings |
| Contact 2 - 3 | 15 | Working winding (smallest) |
| Contact 1 - 3 | 30 | Starting winding (average) |
Based on the table, contact 2 is common. Between pins 2 and 3 the resistance is minimal (15 Ohms) - this is the working winding. Accordingly, between 1 and 3 is the starting one. This technique works for 99% of single-phase compressors.
Table of typical resistance values
Knowledge of the approximate resistance ranges helps to quickly navigate the instrument readings. Values may vary depending on motor power, winding temperature (cold or hot) and manufacturer. Below are indicative data for popular brands.
It is important to understand that a spread of values of 10-20% is normal. If your device shows 25 ohms instead of 20 ohms, this is not a reason to panic. Critical is either a complete absence of resistance (break) or a value tending to zero (short circuit).
| Brand / Model | Working winding (Ohm) | Starting winding (Ohm) |
|---|---|---|
| Atlant (MHM) | 12 – 18 | 25 – 35 |
| Indesit / Ariston | 10 – 15 | 20 – 30 |
| Beko / Samsung | 8 – 14 | 18 – 28 |
| LG (classic) | 15 – 22 | 30 – 45 |
⚠️ Attention: If the multimeter shows a resistance of less than 1-2 Ohms, this may indicate an interturn short circuit. Such a compressor will get very hot and knock out the circuit breaker.
Checking for housing breakdown and interturn short circuit
After identifying the pins, you need to ensure the integrity of the insulation. A breakdown on the housing is a dangerous malfunction that can lead to electric shock when touching the metal parts of the refrigerator. To check, switch the multimeter to the continuity mode or measure the maximum resistance (2 MOhm and higher).
Press one probe to any contact on the compressor, and the second to a cleaned place on the copper tube or metal engine body (where there is no paint). The device should show infinity (one in the most significant digit or no squeak). If a squeak is heard or the arrow deviates, the insulation is broken, operating such a unit is prohibited.
An indirect sign of an interturn short circuit can also be a burning smell or rapid heating of the housing when turned on for a short time. However, an accurate diagnosis of an interturn short circuit is made only with the help of special instruments that measure current consumption, since it is difficult to see the loss of several turns with a conventional tester.
Connection diagram and test run
When the conclusions are determined, you can assemble a circuit for testing. The starting relay is installed strictly in a certain position (usually with an upward arrow), since there is a movable core inside it that must fall under the influence of gravity. A mixed up relay will not work and may burn out.
Connect the wires according to the previously determined diagram: the common wire goes to the network zero, the working winding goes to the phase through the thermal relay, the starting winding goes through the starting device. For a short-term test run, you can use a button connected in parallel to the starting relay to simulate its operation.
Plug the circuit into the network. The compressor should start with a characteristic hum. If a hum is heard, but the shaft does not rotate, and after 5-10 seconds the thermal protection is triggered, the piston may be jammed or the starting winding is faulty. In this case, it is better to stop further experiments.
What to do if the compressor hums but does not start?
A common cause is a malfunction of the starting relay or capacitor (if there is one). Try replacing the relay with a known good one. If this does not help, the compressor may have seized due to lack of oil or mechanical wear. In this case, the “wedging” method by applying increased voltage helps, but this is a risky procedure.
Is it possible to use a compressor with three wires of the same color?
Yes, the color of the insulation does not matter. The main thing is to correctly determine the resistance between pairs of wires. The method of measuring three pairs and finding a common point (the sum of the other two resistances) works regardless of the color of the wires.
Why does the starting winding burn out more often than the working winding?
The starting winding is made of a thinner wire and is not intended for long-term operation. If the starting relay “sticks” and does not open the circuit after starting, the current continues to flow through the thin wire, causing it to instantly overheat and burn out.