How to ring the windings of a refrigerator compressor

A sudden stop in the operation of a refrigeration unit often takes you by surprise, making you nervous because of the risk of food spoilage. One of the first suspicious signs of a malfunction is the absence of the characteristic hum of the motor when plugged in, or attempts to start, accompanied by clicks and subsequent shutdown. In such a situation, it is necessary to carry out an initial diagnosis of the electrical part of the engine in order to exclude its turn-to-turn short circuit or breakage.

The testing procedure, known among craftsmen as “diagnosis”, requires a minimum set of tools and basic knowledge of electrical engineering. Multimeter becomes the main tool in the hands of a home craftsman, allowing you to determine the integrity of circuits with high accuracy. If you are ready to approach the matter carefully, you will be able to identify the problem yourself, without resorting to an expensive call to a specialist for simple diagnostics.

However, it is worth immediately defining the limits of what is possible: a continuity test will only show the electrical integrity of the windings, but will not answer the question about mechanical jamming of the piston group. However, this is a critically important stage, without which further repairs are meaningless. Understanding how to correctly measure resistance and interpret the readings of the device will help you make the right decision about replacing or restoring the unit.

Preparation for diagnostics and safety measures

Before starting any work with the electrical equipment of the refrigerator, it is necessary to ensure complete safety. The first and most important step is to disconnect the unit from the power supply. Don’t just turn off the button if there is one, but physically remove the plug from the socket. Any manipulation under voltage is strictly prohibited and can lead to electric shock or failure of the measuring device.

After turning off the power to the refrigerator, you need to gain access to the compressor. It is usually located in the lower rear part of the housing, in the so-called “crankcase”. You will need to remove the protective cover, which may be secured with latches or screws. In some models Indesit or Atlant access may be slightly difficult due to the housing design, but, as a rule, it is enough to unscrew a few bolts.

⚠️ Attention: Before removing the crankcase cover, make sure that the capacitor, if it is brought out or accessible, discharged. Although in modern circuits discharge occurs quickly, it would not hurt to play it safe and short the capacitor contacts with an insulated tool (for example, pliers with insulated handles) to avoid electric shock.

When access is open, inspect the compressor visually. There should be no obvious signs of burning, melted wires or oil leaks in the area of ​​the electrical connector. If everything is visually clean, you can proceed to preparing the instrument. You will need multimeter (tester), a screwdriver for removing the terminal box and possibly pliers.

Set the multimeter to resistance measurement mode (indicated as Ω or Ohm). Select a measurement limit of 200 ohms or 2 kohms, since winding resistances typically range from 10 to 100 ohms. If the device shows “1” or “OL” on the display with the probes open, it is ready for operation.

Removing the start-protective relay and access to the contacts

To ring the windings, you need to disconnect the start-protection relay. This small plastic block fits directly over the compressor terminals and is connected to the power wires. Carefully remove the retaining bracket or bend the spring clips that hold the relay to the motor housing.

After removing the relay, you will see three contacts coming out of the compressor housing. They are arranged in a triangle. It is important to understand that these pins are not directly marked on the metal, so identifying them is a key step. The relay itself often has markings or a diagram indicating which contact is responsible for what, but it is better to double-check by dialing, since the relay could have been replaced earlier.

The three pins form a triangle, where the vertices are common wire, starting winding and working winding. Depending on the compressor manufacturer (for example Secop, LG, Embraco), the location of the contacts may vary, but the principle of their operation is the same. Usually the common contact is located separately, and the other two are nearby, but you cannot rely only on geometry.

Clean the contacts from oxides if they are darkened using fine sandpaper or eraser Poor contact of the multimeter probes with the terminals can give false readings, and you mistakenly diagnose a break where there is none. The reliability of the connection of the probes with the metal is the key to accurate measurement.

Identification of compressor pins

Before drawing conclusions about the malfunction, you need to determine exactly which pin is responsible for what. There is a universal resistance identification method that works for most single-phase asynchronous motors used in household refrigerators. Between any two contacts you will measure the resistance.

Take a multimeter and take three measurements between pairs of contacts (let's call them 1-2, 2-3, 1-3). Record the resulting values. The logic here is simple: the greatest resistance will be between the starting and working windings (since they are connected in series through a common point inside). The lowest resistance is between the working winding and the common wire.

Why are the resistances different?

The starting winding is wound with a thinner wire and has more turns to create a phase shift at start, so its resistance is always higher than that of the working winding, which is designed for constant operation.

Algorithm The definition is as follows:

• 🔌 Find a pair of contacts with maximum resistance - these are the ends of the starting and working windings. The third, remaining contact is common.
• ⚡ Measure the resistance between the common contact and the other two. The contact where the resistance is lower belongs to the working winding.
• 🚀 The remaining contact, where the resistance is greater (but less than the sum of the previous two), is the starting winding.

For clarity, we give approximate resistance values for a typical compressor with a power of about 100-120 W, that actual figures may differ depending on the model and manufacturer, but the proportions remain similar.

Remember the location of the pins or mark them with a marker/sticker so as not to be confused during assembly. An error in the connection can lead to burnout of the windings or failure of the starting relay. It is critically important not to confuse the starting and operating windings when checking the relay, since applying voltage to the starting winding in a constant mode will lead to its rapid burnout.

Procedure for testing the windings multimeter

Now that the pins have been identified, we move on to directly diagnosing the condition of the windings. The main goal is to ensure that there are no breaks or interturn short circuits. Switch the multimeter to resistance measurement mode (limit 200 Ohms).

Attach the probes to the “Common” and “Working” contacts. The device must show a specific numerical value (for example, 15 ohms). If “1” (infinity) lights up on the screen, it means the circuit is in break. This may indicate a burnt-out wire inside the winding or burnout of a contact inside the housing, which happens less frequently.

Then measure the resistance between the “Common” and “Start” contacts. Here the value should be higher than that of the working winding. Again, an infinity reading indicates a break in the starting winding. Often it is the one that burns out first due to the thinner wire and high starting currents.

The third stage is checking for turn-to-turn short circuit. This is a more complex defect that is not always visible visually. If the winding resistance is significantly lower than normal (for example, 2-3 Ohms instead of 20), this is a sign of a turn short circuit. In this state, the compressor will get very hot, hum and knock out the circuit breaker, even if the circuit is not formally broken.

It is also necessary to check that there is no short circuit to the housing. Press one multimeter probe to any copper pipe of the compressor (after first stripping the small area down to metal, if there is paint), and the second - alternately to each of the three terminals. The device should show infinity. If there is at least some resistance, the compressor is “broken” and operating it is deadly.

⚠️ Attention: If you find a breakdown in the case (even the slightest resistance between the terminals and the case), further operation of the refrigerator is prohibited! This poses a direct threat to people's lives and can lead to fire.

Analysis of results and search for hidden defects

The obtained figures require correct interpretation. The ideal situation is when all three measurements (General-Working, General-Starting, Working-Starting) give stable values, and the sum of the first two is equal to the third. This indicates that the electrical part of the motor is intact.

However, if the compressor hums but does not start, and the continuity test shows normal, the problem may not be in the windings, but in start relay or mechanical jamming. The relay could “stick” or lose its properties, not giving a starting impulse. Checking the relay is a separate procedure, but often replacing this inexpensive element solves the problem.

An interturn short circuit is insidious in that a standard multimeter may not see it if the short circuit occurs only under load or when heated. In such cases, the method of checking current consumption with current clamps is used, but this is already a level of professional diagnostics. For a home master, the signal is an abnormally low resistance (several times less than the rated value) and rapid heating of the case when turned on for a short time.

If the resistance of the starting winding is 2-3 times higher than the norm, this is also a bad sign. An increase in resistance may indicate poor contact inside the winding or the beginning of the process of wire destruction, which will soon lead to a complete break. In such cases, the compressor resource can be considered exhausted.

Typical diagnostic errors

Often, beginners make mistakes that lead to false conclusions. One of the most common is measuring resistance with dirty or oxidized probes. Make sure the tip of the probe fits snugly against the metal of the terminal. Trembling hands or poor contact will give jumping numbers.

Another mistake is trying to ring the compressor without disconnecting the wires from the relay. There may be parallel circuits in the circuit that will distort the readings. Always remove the relay completely, leaving only three “legs” of the compressor free for measurements.

Do not ignore the engine temperature. The resistance of copper depends on temperature. A cold compressor and a hot one will show different values. The norm is to measure on a cold engine. If you have just tried to start the refrigerator, let it cool for at least 30-40 minutes before checking.

It is also a mistake to assume that if the windings are intact, then the compressor is 100% operational. Mechanical defects (piston scuffing, lack of compression) cannot be detected with a multimeter. For this you need a manifold. But electrical testing is the first and mandatory filter, eliminating more than 50% of faults.

Frequently asked questions (FAQ)

Is it possible to restore a burnt winding at home?

Theoretically, it is possible to rewind a compressor, but in practice it is economical inappropriate. Requires specialized equipment for winding, drying and vacuuming. The cost of labor and materials will exceed the price of a new compressor. It is easier and more reliable to buy a new unit or a used one in good condition.

Why does the multimeter show zero Ohm?

The reading “0” or close to it (0.1-0.5 Ohm) between the terminals of the windings indicates a short circuit. This means that the turns have short-circuited, bypassing the resistance of the wire. Such a compressor must be replaced, it cannot be used - it will instantly knock out the machine or burn out.

Does the brand of the refrigerator affect the resistance of the windings?

Yes, it does. Compressors from different manufacturers (Danfoss, LG, Whirlpool) and different capacities have different rating resistances. However, the proportion remains the same: the starting winding always has greater resistance than the working winding. Exact data can be found in the technical documentation (datasheet) for a specific motor model.

What to do if the windings are intact, but the refrigerator does not work?

If the electrical part is normal, check the starting relay (the thermal relay or posistor often fails). If the relay is also working properly, there is likely a mechanical failure of the compressor (jamming) or a freon leak, which is why the thermostat does not give the start command. A more in-depth diagnosis with a pressure gauge is required.