A sudden stop of the refrigerator is always stress, because food supplies are at risk. Often the reason for the silence of the unit is a failure compressor, which is the heart of the entire cooling system. Before calling a technician or buying new equipment, it makes sense to conduct an initial diagnosis of the engine electrical circuit.
The testing process, popularly known as “continuity testing,” allows you to determine the integrity of the windings and the absence of a short circuit to the housing. To perform this procedure, you will need a minimum set of tools, including multimeterand compliance with basic electrical safety rules. In this article, we will analyze each stage of the test in detail so that you can accurately determine the cause of the breakdown.
It is worth understanding that diagnostics does not always guarantee successful repair, since some defects are detected only under load. However, if the multimeter shows a break or breakdown, further operation of the device is impossible without replacing the unit. Let's look at how to properly prepare the equipment and take measurements.
Necessary tools and safety measures
Before starting any work with electrical appliances, you must ensure your safety. Working with high voltage requires caution, and improper handling of the tool may result in electric shock or damage to the refrigerator's electronics. First of all, you need to completely disconnect the device from the power supply by unplugging the plug from the socket.
To carry out high-quality diagnostics, you will need multimeter (a tester) capable of measuring resistance in the range from 0 to 2000 Ohms. It is advisable to use a device with sound indication, as this allows you not to be distracted by the screen while working. You will also need screwdrivers to remove the protective cover of the compressor and insulating tape.
⚠️ Attention: It is strictly forbidden to measure resistance on the windings while the compressor is connected to the network or is under voltage. This will instantly damage your meter.
It is important to ensure good access to the back of the refrigerator. If the unit is built-in, it will have to be partially dismantled or pulled out of the niche. Make sure there is enough lighting in the work area to distinguish wire colors and contact markings.
Access to the electrical part of the compressor
To get to motor contacts, you must remove the rear protective cover located at the bottom of the refrigerator. It is usually secured with latches or a few screws. After removing the cover, you will see a black cylindrical or pear-shaped tank - this is the compressor.
A copper tube approaches it on one side, and on the other there is an electrical block with wires, covered with a plastic casing. This casing must be carefully removed by first snapping the latches or unscrewing the clamp. Inside you will find starting relay and thermal relayput on the pins of the compressor.
To check the windings, you need to remove the starting relay. It is usually held in place by its own weight and a tight fit. Gently pull it down to release the three motor contacts. Do not use excessive force to avoid damaging the fragile controls.
- 🔧 Unplug the refrigerator and remove the back panel.
- 🔌 Remove the plastic casing from the electrical part of the compressor.
- 📉 Carefully remove the start relay from the pins engine.
- 👀 Visually inspect the contacts for oxidation or carbon deposits.
Now you have direct access to the three winding contacts. They can be arranged in a triangle or in a row. It is important not to confuse their purpose, although this is not critical for the initial connection to a break. The main thing is to ensure clean contact of the multimeter probes with the terminals.
Determination of the motor winding circuit
Before picking up a multimeter, it is useful to understand what exactly we are dealing with. Most household refrigerators use single-phase asynchronous motors with a starting winding. Such motors have three terminals: two for working winding and one for the starting.
The working winding is made of a thicker wire and has less resistance, since it works constantly. The starting winding is wound with a thin wire, has a higher resistance and is turned on only for a short time to accelerate the rotor. The third contact is common for both windings.
Why do the windings have different resistance?
The difference in resistance is due to the physics of the engine. The working winding creates the main magnetic field, and the starting winding creates a phase shift to create torque.
Sometimes you can find an electrical diagram on the compressor housing or in the documentation, where the contacts are designated by letters. For example, C (Common) - general, R (Run) - working, S (Start) - starting. In European models, the markings may be different: C, M (Main), A (Auxiliary).
If the markings are erased or missing, the purpose of the pins can only be determined by measuring the resistance between them. Knowing the typical resistance values for different models, you can accurately identify contacts without a circuit.
| Parameter | Working winding | Starting winding | Common contact |
|---|---|---|---|
| Resistance | Low (10-30 Ohm) | High (30-60 Ohm) | Sum of resistance |
| Wire thickness | Thick | Thin | - |
| Operating mode | Permanent | Short-term | - |
| Wire color (often) | Red/Blue | Green/Yellow | White/Black |
Understanding this structure is necessary for correct interpretation of the tester readings. If you mix up the windings, the motor may hum, but not start, or the starting device will burn out.
The procedure for testing with a multimeter
Now we move on to the most important stage - direct measurements. Switch the multimeter to resistance measurement mode (indicated by the Ω icon) to the 2000 Ohm (2kOhm) limit. If the device has a “dialing” mode with sound, you can use it, but digital resistance values are more informative.
Apply the probes to any two of the three available contacts. Record the reading. Then move the probes to another pair of contacts and record the result again. As a result, you should have three measurements between different pairs of contacts. This will allow you to build a complete picture of the condition of the engine.
Sequence of measurements:1. Contact 1 ↔ Contact 2
2. Contact 2 ↔ Contact 3
3. Contact 1 ↔ Contact 3
Analyze the numbers obtained. The sum of the resistances of the two smaller values should be equal to the third, largest value. For example, if there is a resistance of 20 ohms between pins A-B, and 40 ohms between pins B-C, then there should be about 60 ohms between A-C. This indicates the serviceability of the windings.
⚠️ Attention: If the multimeter shows infinity (one on the left of the screen) between any two contacts, this means a winding break. Repair in this case is impossible; the compressor needs to be replaced.
It is also important to check that there is no short circuit to the housing. Switch the tester to the maximum resistance measurement limit (20 MΩ) or to diode test mode. Press one probe to the cleaned area on the compressor body (where there is no paint), and with the second touch each of the three contacts in turn.
The device should show infinity. If you see any resistance values or hear a squeaking noise, a problem has occurred insulation breakdown to the body. Operating such a refrigerator is deadly, since a voltage of 220 Volts may appear on the metal body.
☑️ Compressor diagnostics
Analysis of results and search malfunctions
After taking readings, it is necessary to correctly interpret the data. The normal resistance of the working winding is usually from 10 to 30 ohms, and the starting winding is from 30 to 60 ohms, although the values may vary depending on the power motor. The main thing is the presence of a clear value and not a break.
If the resistance is significantly lower than normal (for example, 1-5 Ohms), this may indicate an interturn short circuit. In this case, the engine will become very hot and knock out the circuit breaker or thermal relay. Sometimes such a malfunction is difficult to detect only by continuity; a test with current clamps under load is required.
Consider typical scenarios that you may encounter:
- ✅ Normal: Three different resistance values, the sum of the two smaller ones is equal to the larger one, infinity rings on the case.
- ❌ Open: The multimeter shows infinity between any contacts. The engine is dead.
- ⚡ Breakdown: There is resistance between the contact and the housing. Danger to life!
- 📉 Short circuit: The resistance is abnormally low, close to zero.
Do not forget about checking the starting relay itself, which you removed. Often the problem lies precisely there, but the motor is working properly. You can check the relay by shaking it near your ear - if you hear a ringing, it means the contacts or core are loose. The relay coil circuit also rings.
Frequent diagnostic errors
Many home craftsmen make mistakes that lead to false conclusions. One of the most common is an attempt to ring the compressor without removing the start relay. In this case, you are measuring resistance through the internal circuitry of the relay, which gives distorted results.
Another mistake is using a faulty or discharged multimeter. Before work, always check the device by connecting the probes to each other - it should show zero or a value close to it. It is also important to press the probes tightly against the contacts, since oxides can create additional resistance.
Some users ignore checking for housing breakdown, believing that if the motor is humming, then everything is in order. This is a dangerous misconception. The current leakage may be small, but it can cause unpleasant sensations when touching the refrigerator or triggering an RCD.
⚠️ Attention: Technical characteristics of compressors from different manufacturers (Indesit, LG, Bosch, Atlant) may differ. The data in the table is average. Always check the official documentation for your specific model.
If after all the checks it turns out that the motor is working, but the refrigerator does not work, the problem may lie in the thermostat, control board or freon leak. In such cases, a more in-depth professional diagnosis is required using a pressure manifold.
Questions and answers (FAQ)
Is it possible to restore a broken compressor winding?
At home - no. Rewinding a refrigerator motor requires special equipment, precise calculation of the number of turns and wire diameter, as well as vacuum drying and oil filling. It is more economically profitable and reliable to buy a new compressor.
Why does the compressor hum, but does not start, although the continuity test showed normal?
Most likely, the start relay is faulty or the compressor piston (hydrocline) is jammed. It is also possible that a starting wedge may occur due to thickened oil if the refrigerator has been standing for a long time. Sometimes gently hammering the case with a hammer through a wooden gasket helps, but this is a temporary measure.
Which multimeter is better to choose for checking a refrigerator?
For household needs, any digital multimeter of the DT830 series or more advanced models like Mastech are suitable. The main requirement is the presence of a resistance measurement mode (Ohm) and a circuit continuity mode with a sound signal.
Is it dangerous to touch the compressor contacts with your hands?
If the refrigerator is unplugged for more than 5-10 minutes, the capacitors are discharged, and there is no direct danger. However, there may be sharp edges of tubes or metal burrs on the body, so it is better to work with gloves.
What to do if the resistance of the windings is very different from the norm?
If the resistance is too high, poor contact inside or a partial break is possible. If it is too low, there is an interturn short circuit. In both cases, the compressor requires replacement, since its operation will be unstable and will lead to network overload.