Refrigerator failure is always stressful, especially when there are perishable foods left in the refrigerator. Often the cause of the breakdown is compressor, which is the heart of the entire cooling system. Before calling a technician or buying a new unit, it makes sense to conduct an initial diagnosis of the electrical part of the motor. This will allow you to understand whether it is possible to revive the old compressor or whether it must be unconditionally replaced.
Checking stator windings is the first and most important stage in identifying a malfunction. For this procedure, you do not need complex laboratory equipment, just a basic set of tools and basic knowledge of electrical engineering. Correctly performed diagnostics will help to avoid unnecessary expenses and accurately determine the nature of the breakdown, be it a banal open circuit or a serious stator winding interturn short circuit. In this article we will analyze in detail the algorithm of actions necessary for safe and accurate testing of the starting and operating windings. You will learn what resistance values are considered normal, how to detect a breakdown in the housing, and what to do if the device’s readings surprise you. A competent approach to checking the engine will save you time and restore confidence in your own abilities when repairing household appliances. turn-to-turn short circuit.
In this article we will analyze in detail the algorithm of actions necessary for safe and accurate testing of the starting and operating windings. You will learn what resistance values are considered normal, how to detect a breakdown in the housing, and what to do if the device’s readings surprise you. A competent approach to checking the engine will save you time and restore confidence in your own abilities when repairing household appliances.
Preparation for diagnostics and safety measures
Any work with electrical equipment requires strict adherence to safety precautions. The first step is to completely turn off the power to the refrigerator by unplugging the power cord from the outlet. Do not rely solely on the body switch or thermostat, as electric current it may remain on the contacts or accidentally come back online. Only physical disconnection from the network guarantees your safety when working with exposed wires.
To conduct high-quality diagnostics, you will need multimeter (tester) capable of measuring resistance (Ohm) and checking the integrity of the circuit. A screwdriver, pliers and electrical tape will also be useful. Before starting work, make sure that the room is dry and your hands are not wet, as humidity significantly reduces skin resistance and increases the risk of electric shock if accidentally turned on.
It is important to provide access to the compressor, which is usually located in the lower rear part of the unit. You will have to remove the protective cover to get to the start relay and motor contacts. Be careful with the copper tubes of the refrigeration circuit: they are very soft and easily damaged, which can lead to freon leakage.
⚠️ Attention: If you notice traces of oil, burning or melted wiring on the compressor, diagnostics may no longer be needed - the engine has physically burned out. In such cases, further operation is impossible.
Before touching the contacts, it is recommended to discharge the capacitors (if they are in the circuit) and allow the engine to cool if it has been running recently. A cold motor will show more accurate winding resistance values, since copper changes its properties when heated.
Compressor pin layout
To correctly ring the windings, you need to clearly understand which contact is responsible for what. The compressor terminal block usually has three terminals arranged in a triangle. They are responsible for the starting winding, working winding and common point. Incorrect identification of contacts can lead to erroneous conclusions about the condition of the engine.
The standard marking of the terminals on the relay body or the compressor itself is often indicated in Latin letters. The working winding is marked as R (Run) or C (Common in some circuits, but more often C is common). The starting winding is designated as S (Start). The common wire is marked C (Common) or L (Line). However, you should not rely only on letters, since manufacturers can use their own standards.
You can determine the purpose of the contacts visually by the thickness of the wires inside the relay itself or by their location relative to each other on the block. Typically, the starting winding has a higher resistance and a smaller wire cross-section, and the working winding has the opposite. Knowing this feature, you can initially find your way even without a diagram.
If you have technical documentation for a specific refrigerator model, for example Indesit or Atlant, be sure to check the electrical diagram. This will eliminate errors, especially in models with inverter compressors, where the pinout may differ from the classic one.
The process of checking the integrity of the windings with a multimeter
The most reliable way to check is to measure the active resistance between the terminals. To do this, switch the multimeter to resistance measurement mode (range 2 kOhm or 200 Ohm). First, touch the common terminal and the working winding terminal with the probes. Record the resulting value. Then repeat the procedure for the common terminal and the starting winding.
The state is considered normal when the sum of the resistances of the starting and working windings (measured separately from the common wire) is equal to the resistance measured between the starting and working terminals directly. If the device shows infinity (1 or OL), this indicates an open circuit. If the resistance is close to zero, there is a short circuit.
It is important to consider that the resistance of the starting winding is always higher than that of the working winding. This is due to the fact that the starting winding is made of thinner wire and has more turns. The working winding must conduct current constantly, so its resistance is lower, which allows the motor to operate efficiently.
☑️ Dialing algorithm
When taking measurements, try not to touch the metal parts of the probes with your fingers, since the resistance of the human body can distort the readings of the device, especially at high sensitivity ranges. Hold the probes only by the insulated handles.
Diagnostics of interturn short circuit and breakdown to the housing
The most insidious malfunction, which is difficult to identify by simple ringing, is interturn short circuit. In this case, the integrity of the winding is not broken, and the device will show some resistance, but some of the turns are closed to each other. This leads to a sharp increase in current consumption, overheating and activation of the thermal relay.
An indirect sign of an interturn short circuit may be an uncharacteristically low winding resistance compared to the passport data or similar serviceable models. This is also indicated by the hum of the motor when trying to start and the instantaneous shutdown of the protective relay. Most accurately, such a malfunction is detected using special testers, but at home you can focus on indirect signs.
Be sure to check that there is no breakdown in the case. To do this, press one multimeter probe to a cleaned area on the metal body of the compressor (you can lightly scratch the paint to make contact), and with the other touch any of the three contacts of the block. The device should show infinity. If there is any resistance, the engine is faulty and dangerous to use.
⚠️ Attention: Operating a compressor with a breakdown in the housing is strictly prohibited. This creates a direct threat to human life when touching the metal parts of the refrigerator.
Sometimes breakdown occurs only when heated. If a “cold” test shows the norm, but the motor knocks out the machine after a few minutes of operation, the problem may lie in the destruction of the winding insulation due to metal expansion.
Analysis of results: table of normal values
Understanding what values are considered normal is critical for correct diagnosis. Resistance depends on motor power, model and manufacturer. Below are indicative data for household refrigeration compressors of medium power.
| Winding type | Resistance range (Ohm) | Characteristic symptoms of malfunction |
|---|---|---|
| Working (R) | 10 - 35 Ohm | Open (infinity) or short circuit (0 Ohm) |
| Starting (S) | 30 - 80 Ohm | Significantly higher than working, open circuit |
| Case | Infinity (∞) | Any value indicates a breakdown |
| Total (R+S) | 40 – 115 Ohm | Inconsistency with the sum of individual measurements |
It is worth noting that the parameters may vary among different manufacturers, such as LG, Whirlpool or Beko. For example, on some models the starting winding may have a resistance of up to 100 Ohms. The main rule: the resistance of the starting winding should always be higher than the resistance of the working winding.
If your measurements differ radically from the table values, this is a sure sign of a defect. However, remember that the multimeter may have an error, especially if its battery runs out. Always check the device with a known resistance or by shorting the probes (should be 0).
Frequent errors during testing and their consequences
One of the most common mistakes is checking without disconnecting the start relay. In some circuits, the relay contacts may bypass the windings, causing incorrect multimeter readings. Always remove the relay from the compressor contact group before starting measurements.
Another mistake is ignoring the state of the contacts. Oxidation or carbon deposits on the terminals can create additional contact resistance, which the tester will perceive as a winding failure. Clean the contacts with fine sandpaper or a file before diagnostics.
Some technicians try to “revive” the engine by applying voltage directly, bypassing the thermal relay. This is extremely dangerous and can lead to a fire if there is a hidden short circuit in the windings. Thermal relay It is there for a reason - it protects the motor from overloads.
⚠️ Attention: Technical characteristics and connection diagrams may vary depending on the year of manufacture and model. Always check the manufacturer's official documentation for your specific modification.
Attempting to start a compressor with a faulty starting winding by applying an external pulse may temporarily revive the unit, but this will only delay its final failure. If the winding is burned out, the motor must be replaced.
FAQ: Frequently asked questions
Is it possible to check the compressor without a multimeter?
It is impossible to qualitatively check the resistance of the windings without a device. However, you can use the "test lamp" method (incandescent lamp in series with the battery) by connecting it to the contacts. A bright glow will indicate the integrity of the circuit, but accurate data on resistance and turn-to-turn closure cannot be obtained using this method.
What to do if the resistance is normal, but the refrigerator does not freeze?
If the electrical part is intact, the problem may be mechanical: a jammed piston, loss of compression or freon leak. It is also worth checking the thermostat and the starting relay, which could have failed, preventing the engine from starting.
Why does it hum, but does not start?
A hum when the rotor does not rotate often indicates a jammed mechanism or a malfunction of the starting winding/relay. The motor tries to start, but there is not enough torque, or the shaft is physically clamped.
Is it dangerous to change the compressor yourself?
Replacing a compressor requires not only electrical knowledge, but also skills in working with the refrigeration circuit (soldering pipes, evacuation, refilling with freon). Without special equipment, it is almost impossible to carry out this procedure yourself efficiently.