The compressor is the “heart” of the refrigerator, and its malfunction often leads to complete failure of the equipment. One of the key tasks in diagnostics is to correctly identify the windings (working, starting and general) to check their integrity, resistance and identify possible breaks or interturn short circuits. Without this step, it is impossible to say for sure whether the compressor is to blame for the breakdown or whether the problem lies in another unit.
In this article we will analyze three main methods identification of the windings: by markings on the case, using a multimeter and visually - by the location of the pins. You will also learn how the connection diagrams differ in compressors of different brands (Danfoss, Embraco, Secop), what resistance values are considered normal, and what to do if the windings “do not connect.” The instructions are suitable for both household refrigerators (Atlant, Indesit, Samsung) and industrial installations.
Before you start work, remember: the compressor stores residual voltage even after disconnecting from the network. Carry out all manipulations no earlier than 10–15 minutes after turning off the refrigerator, using tools with insulated handles.
1. Why is it important to correctly identify the compressor windings
Incorrect winding identification is one of the main reasons false diagnoses when repairing refrigerators. For example, if you confuse the starting and operating windings when testing, you may mistakenly decide that the compressor has burned out, although in fact the problem is in the relay or thermostat. Here are the key situations when accurate determination of windings is critical:
- 🔧 Fault diagnosis: without checking the resistance of the windings, it is impossible to distinguish an interturn short circuit from an open circuit.
- 🔄 Replacing the compressor: when connecting a new unit, you need to correctly connect the terminals to relay, otherwise the motor will not start or will burn out.
- ⚡ Checking the starting relay: if the relay does not work, first check the integrity of the compressor windings.
- 📊 Selection of an analogue: when buying a used compressor, know the resistances windings helps to verify its performance.
Most modern compressors (Embraco EG, Danfoss NL, Secop SC) have three outputs: C (common), S (starting), R (worker). However, in older models (Soviet KV-6, "Donbass"), there may be no markings, and there are four or even five pins. In such cases, you cannot do without a multimeter.
⚠️ Attention: If the compressor was previously repaired, its windings could have been re-soldered. In this case, standard connection diagrams do not apply - rely only on the multimeter readings.
2. Method 1: Determining the windings by markings on the housing
The easiest way is to find technical tag on the compressor. It is usually located on the top of the case or on the side, under the mounting bolts. The tag indicates:
- 📋 Compressor model (for example, Embraco EGX 90HLC or Danfoss NL 12FX).
- 🔢 Pin connection diagram with designations
C,S,R. - ⚡ Rated current values and power.
If the tag is saved, just check the manufacturer's documentation. For example, the common terminal ( Embraco general conclusion (C) is always located in the middle, and the one on the left (if you look at the connector) Below is a table with typical circuits for popular ones. brands: Danfoss — on the left (if you look at the connector). Below is a table with typical patterns for popular brands:
| Brand | Model range | Pin location (from left to right) | Winding resistance (Ohm) |
|---|---|---|---|
| Embraco | EG, EGX, EMB | S — C — R |
Starting: 15–30 Working: 5–15 General: 10–20 |
| Danfoss | NL, NT, NS | C — S — R |
Starting: 20–40 Working: 8–20 General: 12–25 |
| Secop (DWM) | SC, SL | R — C — S |
Startup: 25–50 Working: 10–25 General: 15–30 |
| Soviet/Donbass | KV, FG | 4 pins (ringing required) | Individually |
If the tag is missing or painted over, proceed to the next method. Also note that in some models (Secop SC15G) the pins may be marked with letters A, B, C - in this case A usually general, and B and C —starting and operating (required to be clarified on the datasheet).
3. Method 2: Testing the windings with a multimeter (step-by-step instructions)
This is a universal method that works even for compressors without markings. You will need multimeter (in ohmmeter mode) and a screwdriver to unscrew the terminals. Follow the algorithm:
- Disconnect the refrigerator from the mains and discharge the capacitors (short-circuit the terminals with a screwdriver with an insulated handle).
- Remove the start relay (usually attached to the compressor with one bolt). Carefully disconnect the terminals, remembering their location.
- Find three pins on the compressor (they can be hidden under a plastic cover).
- Ring all pairs of pins:
- 🔹 There should be resistance between two pins minimum (usually 5-30 Ohms) - these are the working and starting windings.
- 🔹 Between the third terminal and each of the first two, the resistance will be average (10–40 Ohms) - this is the common terminal (
C). - 🔹 Between the working and starting windings the resistance is equal to the sum of the resistances each of them to the common output.
Example: if when calling you received the values R-C = 10 Ohm, S-C = 20 Ohm and R-S = 30 Ohm, then:
C— common terminal (average resistance).R— working winding (smaller Resistance). short circuit) orS- starting winding (higher resistance).
Disconnect the refrigerator from the network|Discharge the capacitors|Remove the start relay|Ring all pairs of terminals|Check the resistance with the norm-->
If the resistance between any terminals equals 0 (short circuit) or infinity (break), the compressor is faulty. Also a dangerous sign is winding resistance difference of more than 50% from the nominal (for example, operating = 5 Ohm, starting = 30 Ohm).
⚠️ Attention: In compressors with built-in overheating protection (for example Embraco Fullmotic) the resistance of the windings can change depending on the temperature. room temperature (20–25°C).
4. Method 3: Visual identification by pin location
If you don’t have a multimeter at hand, you can rely on standard pin layouts. Most compressors have three pin connectors arranged in a triangle or line. Here are the typical options:
- 🔺 Triangle:
- Top pin -
C(general). - Bottom left -
S(starting). - Bottom right -
R(working).
- Top pin -
- 📏 Line (from left to right):
- Embraco:
S — C — R. - Danfoss:
C — S — R. - Secop:
R — C — S.
- Embraco:
For compressors with four terminals (old Soviet models) usually:
- The two extreme ones are the working and starting windings.
- The two middle ones are the common terminal and the thermal protection terminal (called a break when the compressor is cold).
The visual method is less reliable than ringing, but it will help in the field. For example, if you are repairing a refrigerator in the country and only have a screwdriver at hand.
5. Typical winding faults and their symptoms
By identifying the windings, you can diagnose specific faults. Here are the most common problems and their symptoms:
| Malfunction | Symptoms | Winding resistance | What to do |
|---|---|---|---|
| Breakage of the working winding | The compressor does not start, it hums | R-C = ∞ |
Replacing the compressor |
| Interturn short circuit | The compressor gets hot, turns off due to protection | R-C or S-C below normal |
Replacement of the compressor |
| Short circuit to the housing | Knocks out the RCD, the compressor “shocks” | Any output - housing = 0 Ohm | Replacement of the compressor |
| Failure of the starting winding | The compressor starts and immediately stops | S-C = 0 or S-C = ∞ |
Replacement or repair of the winding (rarely) |
Critical point: if the resistance between any winding terminal and the metal body of the compressor is less than 500 kOhm, the compressor is dangerous for use - it must be replaced. Such a malfunction leads to electric shock and fires.
Also pay attention to wire insulation colorgoing to the relay:
- 🔴 Red/orange - usually the working winding.
- 🔵 Blue/black - starting winding.
- 🟢 Green/yellow - general conclusion.
⚠️ Attention: In compressors with inverter control (for example, LG Linear Compressor) the windings may have non-standard resistance (up to 100 Ohms). To diagnose them, an oscilloscope or a specialized tester is required.
6. Common mistakes when determining windings
Even experienced craftsmen sometimes make mistakes that lead to false conclusions. Here's what you can't do:
- 🔌 Ringing the energized windings —it will lead to damage to the multimeter and electric shock.
- 🔄 Swap the starting and working windings —the compressor will not start and the relay will burn out.
- 📉 Ignore the compressor temperature —the resistance of the windings changes when heated.
- 🔧 Bend or damage the conclusions —this may lead to a break inside the housing.
Another common mistake is do not take into account the type of compressor. For example, in hermetic compressors (as in most household refrigerators) the windings are filled with oil, and their resistance may increase over time due to oxidation. In semi-hermetic (industrial installations) the windings are open and can be cleaned or repaired.
If you If you doubt the dialing results, repeat the measurements 2-3 times or use another multimeter - sometimes the fault lies in the device itself.
7. Practical tips for repair
If you find out that the compressor windings are faulty, here's what you can do:
- 🔧 Replacement of the compressor is the most reliable option. A new compressor is selected according to:
- Refrigerant (R134a, R600a, R290).
- Power (hp or kW).
- Mounting type (flange, thread).
- 🔄 Repair of windings —possible only for semi-hermetic compressors. Requires rewinding and impregnation with varnish.
- ⚡ Checking the relay and capacitor —often the problem is not in the compressor, but in the starting device.
When replacing a compressor, be sure to:
- Drain the oil from the old and new compressors, mix and fill it back (if the oil types are compatible).
- Rinse the refrigerant system (if the compressor is burned out, there may be oil decomposition products in the tubes).
- Fill the refrigerator with refrigerant, taking into account the length of the pipeline.
If you have never refilled freon, it is better to entrust this to a specialist - errors in evacuation or refrigerant dosage will lead to repeated failure.
How to check the start relay without a compressor?
Connect the relay to a working compressor with known windings. If the compressor does not start or the relay gets hot, it is faulty. You can also ring the relay contacts manually: when voltage is applied to the coil, they should close.
FAQ: Frequently asked questions about compressor windings
❓ Is it possible to determine the windings without a multimeter?
Yes, but only visually - according to the standard pin layout (see section 4). However, this method is unreliable, especially for old or unmarked compressors, you risk making a mistake with the relay connection, which will lead to failure of the compressor.
❓ What winding resistance is considered normal?
Normal values depend on the compressor model:
- Embraco EGX: working - 5-15 Ohms, starting - 15-30 Ohms.
- Danfoss NL: working - 8-20 Ohms, starting - 20–40 Ohm.
- Soviet HF: working - 10-25 Ohm, starting - 25-50 Ohm.
If the resistance differs by more than 30% from the nominal value, the compressor is faulty.
❓ What to do if the resistance between the terminals is zero?
Zero resistance between any the terminals (except for the case when you measure the working + starting windings through the common terminal) means short circuitThe compressor must be replaced. If zero is only between the working and starting windings. starting windings (if correctly connected to the common terminal), this is the norm - as it should be.
❓ Why does the compressor hum, but does not start?
There may be reasons as follows:
- Faulty starting winding (check the resistance
S-C). - Burnt starting relay (ring the contacts).
- Stuck piston compressor (you need to turn the shaft manually).
- Low voltage in the network (less than 190 V).
❓ Is it possible repair burnt windings?
In compressors (most household refrigerators), repairing the windings is impossible - they are filled with oil and sealed. In hermetic In compressors (most household refrigerators), repair of the windings is impossible - they are filled with oil and sealed. IN semi-hermetic (industrial installations), you can rewind the windings, but this is expensive and requires special equipment. compressor.