Testing the refrigerator compressor with a multimeter: instructions for self-diagnosis

When the refrigerator stops freezing, but the light inside is on and the fan is working, the first thought is: the compressor is broken. However 90% of such cases they are not associated with motor failure, but with problems in the power circuit, start-up relay or freon leak. Before taking your equipment to a service center or buying a new unit, it’s worth check the refrigerator compressor with a multimeter -it will take 15 minutes and save thousands of rubles.

In this article you will find step-by-step instructions with photo, how to properly check the compressor windings, what resistance values are considered normal for different models (Atlant, Indesit, Samsung, LG etc.), as well as a unique table of correspondence between multimeter readings and types of faults. We will look at how to distinguish an interturn short circuit from a winding break, and what to do if the tester shows “infinity.”

Important: compressor diagnostics require minimal skills in working with electrical appliances. If you have never held a multimeter in your hands, it is better to entrust the test to a specialist. But if you are ready to act carefully, follow our recommendations.

1. Preparing for the test: tools and safety measures

Before ringing the compressor, make sure that the refrigerator disconnected from the network is at least 30 minutes. This is necessary so that the capacitors in the power circuit are discharged - they can hold dangerous voltage even after the device is turned off. Also prepare:

• 🔧 Multimeter (any model with an ohmmeter mode is suitable, even the cheapest one for 300 rubles).
• 🔌 Phillips screwdriver (for removing the compressor protective casing).
• 📸 Smartphone (to photograph the location of the wires before disconnecting).
• 🧤 Rubber gloves (protected from accidental electric shock when working with contacts).

The compressor is usually located at the bottom of the refrigerator, under the plastic panel. For models No Frost it can be hidden behind the back wall. To get to the terminals, remove the protective casing (it is secured with 2–4 self-tapping screws). Under it you will see three outputs marked:

• C (Common) - general output;
• S (Start) - starting winding;
• R (Run) - working winding.

⚠️ Attention: If there is no marking on the compressor or it is erased, do not try to guess the location of the terminals this may lead to false readings. In this case, find the compressor model (written on the sticker) and look at the diagram on the Internet.

Before disconnecting the wires take a photo of their location - this will help you connect everything back correctly later. If the wires are already disconnected (for example, during a previous repair), remember: C always goes to the start-up relay, and S and R to the windings.

2. Multimeter connection diagram: which contacts to dial

The refrigerator compressor has three windings, but only pairs of contacts are dialed together. Below is a diagram of how to correctly connect the multimeter probes:

Important: resistance values may differ slightly depending on the compressor model. For example, y Danfoss the working winding usually shows 10–15 Ohm, and y Embraco — 5–10 Ohm. Look for exact data in the technical documentation for your model.

If, when testing any pair of contacts, the multimeter shows:

• 🔢 0 Ohm —short circuit between the windings;
• 🔢 1 (infinity) —open circuit;
• 🔢 The value is outside the norm (for example, S→R = 5 Ohm, although it should be ~30) - interturn short circuit.

⚠️ Attention: If the compressor it buzzes, but does not start., the problem may not be in the windings, but in start-up protection relay. Before testing, check whether the relay is “sticking” - to do this, shake it: if you hear a knock, the part is faulty.

Disconnect the refrigerator from the network for 30+ minutes|

Remove the compressor protective casing|

Take a photograph of the location of the wires|

Disconnect the wires from terminals C, S, R|

Switch the multimeter to ohmmeter mode (200 Ohm)-->

3. Step-by-step instructions: how to test a compressor with a multimeter

Follow this algorithm to correctly check the windings:

1. Step 1. Install on the multimeter, resistance measurement mode (Ω) with a range 200 Ohm.
2. Step 2. Connect the probes to the terminals C i S (start winding). Record the readings. Norm: 15–40 Ohm.
3. Step 3. Connect the probes to C i R (working winding).Normal: 5–20 Ohm.
4. Step 4. Connect the probes to S i R. equal to the sum of the values ​​from steps 2 and 3 (an error of ±5 Ohms is allowed).
5. Step 5. Check insulation: one probe on any terminal, the second on the metal body of the compressor Normal: ∞ (infinity). If there is any resistance, the compressor “breaks through” the housing and requires replacement.

Example of correct readings for compressor Embraco EG80HLE:

• C→S = 28 Ohm;
• C→R = 12 Ohm;
• S→R = 40 Ohm (28 + 12).

If at least one of the values is not normal, the compressor is faulty. do not rush to change it - sometimes the problem lies in oxidized contacts. Try cleaning the terminals with fine sandpaper and ringing again.

4. Typical compressor malfunctions and their symptoms

Depending on the multimeter readings, you can diagnose a specific one. breakdown. Below is a table with a breakdown of the test results:

If the compressor hums, but does not startthe problem may not be in it, but in:

• 🔋 Start protection relay (most often);
• 🔌 Thermostat (does not give a start signal);
• ❄️ Freon leakage (the compressor works, but does not freeze).

To eliminate these faults, check:

• 🔊 Relay: shake it - if you hear a knock, it is faulty;
• 🔍 Thermostat: close its contacts directly (if the refrigerator works, the thermostat needs to be replaced);
• 🧊 Freon: if the compressor is running, but the condenser (grid at the back) does not heat up, there is a leak.

How to check the start-up relay without a multimeter?

If the compressor hums but does not start, turn off the refrigerator, remove the relay and shake it. A working relay makes a clear click when turned over. If there is no click or a knocking noise is heard (as if something is loose inside), the relay is faulty and needs to be replaced. The cost of a new part is from 500 to 1500 rubles.

5. Frequent errors when testing a compressor

Even experienced technicians sometimes make mistakes when diagnosing. Here's what you can't do:

• 🚫 Ring the compressor under voltage. This is not only dangerous, but also distorts the readings. Always unplug the refrigerator!
• 🚫 Ignore terminal markings. If you confuse S and R, you may misinterpret the results.
• 🚫 Use a faulty multimeter. Before checking, short-circuit the probes - the device should show 0 Ohm.
• 🚫 Ring the compressor immediately after operation. Let it cool for 30–60 minutes, otherwise the readings will be inaccurate.

Another common mistake is do not check the insulation on the case. If the compressor fails, it is life-threatening! Be sure to attach one probe to any terminal, and the second to the metal body of the motor. Norm: ∞ (infinity).

If you doubt the results, repeat the test 2-3 times or use another multimeter. It is also useful to compare the readings with the data from the technical data sheet of the compressor (they can be found by model on the Internet).

⚠️ Attention: If the compressor is starts, but turns off after 5-10 seconds, the problem may be in overheating. In this case, check whether the ventilation grille on the back wall of the refrigerator is not clogged, and whether it is operating in a room that is too hot (the optimal temperature is 16–32°C).

6. What to do if the compressor is faulty?

If the test shows that the compressor is faulty, you have three options:

1. Replacement of the compressor. A new motor costs from 5,000 to 15,000 rubles depending on the model. It is better to entrust the replacement to a specialist, as required evacuating the system and refilling with freon.
2. Compressor repair. In some cases (for example, if a wire breaks inside) the motor can be restored. The cost of repairs is from 3,000 rubles.
3. Buying a new refrigerator. If your unit has more than 10–15 years, replacing the compressor may be unprofitable. Modern models (Atlant New Wave, LG Inverter) consume. 2 times less electricity.

Before making a decision, evaluate the condition of the refrigerator in In general:

• 🔄 If it is it freezes well, but the compressor is noisy - it may be enough to change the oil or clean the system.
• ❄️ If it doesn’t freeze, but the compressor works - most likely there is a freon leak (repair will cost 2,000–4,000 rubles).
• 💥 If compressor burned out (blackened, smells like burning) - only replacement.

Cost of work in service centers:

If you decide to replace the compressor yourself, please note: you will need special equipment (vacuum pump, pressure gauge station) and skills to work with freon. Without this, the new compressor will quickly fail.

7. compressor

To make the refrigerator compressor last longer, follow these recommendations:

• 🔌 Do not connect the refrigerator through an extension cord. Power surges are the main cause of winding burnout. Use surge filter or a stabilizer.
• 🧊 Do not place the refrigerator next to the radiator or stove. Overheating of the compressor reduces its service life by 2-3 times.
• 🧹 Clean the condenser (grid at the back) every six months. Dust worsens heat transfer, and the motor is overloaded.
• ❄️ Do not overload the freezer. If the food is tightly packed, the compressor takes longer to build up cold.
• 🔄 Defrost the refrigerator with a drip system once every 6 months. Ice on the evaporator causes the compressor to work without stopping.

Also avoid frequent on/off the refrigerator - this creates peak loads on the windings. If there is unstable voltage in your area, install voltage control relay (costs from 2,000 rubles).

Average compressor life - 10–15 yearsIf your refrigerator runs longer, be prepared for the fact that the motor may fail. In this case, replacement is often unprofitable, and it is better to consider purchasing new equipment.

FAQ: Frequently asked questions about compressor dialing

Is it possible to dial compressor without removing it from the refrigerator?

Yes, but to do this you need to disconnect the wires from the terminals C, S and R. The main thing is to wait for the capacitors to discharge (30 minutes). dismantling. disconnect the refrigerator from the network and wait for the capacitors to discharge (30 minutes). Testing “in place” gives the same results as after dismantling.

The multimeter shows 0 Ohm between all terminals. What does this mean?

This is short circuit between the windings. The compressor cannot be repaired - only replacement. due to power surges or overheating.

The compressor hums, but does not start. What is the reason?

In 80% of cases, start-protection relayAlso check:

• 🔌 Thermostat (close the contacts directly - if the refrigerator starts working, the thermostat is faulty);
• 🔋 Capacitor (if it is swollen or liquid leaks, replacement is required);
• ⚡ Network voltage (if it is lower 190 V, the compressor will not start).

What resistance should it have refrigerator compressor Atlant?

For most models Atlant (with compressors Danfoss or Secop) normal values:

• C→S = 20–35 Ohm;
• C→R = 10–15 Ohm;
• S→R = 30–50 Ohm.

Look for exact data by compressor model (it is indicated on the sticker).

Is it possible to repair a compressor with an interturn short circuit?

Theoretically yes, but in practice it is unprofitable. Repairs will cost 70–80% the cost of a new compressor, and there is no guarantee that it will last a long time. It is better to replace the motor or the refrigerator.