Checking a refrigerator motor with a multimeter: a complete guide with diagrams and standards

When the refrigerator stops freezing, makes strange sounds or refuses to turn on at all, the first thought is that the compressor is broken. But before you take your equipment for service or buy a new unit, you should check the engine (compressor) yourself using a conventional multimeter. This procedure does not require professional skills, but will help save hundreds of rubles on diagnostics.

In 80% of cases, refrigerator malfunctions Indesit, Atlant, Samsung or LG are associated with broken windings, an interturn short circuit or a breakdown to the housing. All these defects are easily detected by the tester - the main thing is to know which contacts to call what values ​​are considered normal. In this article you will find step-by-step diagrams for different types of compressors, resistance tables and practical tips for interpreting the results.

Important: diagnostics with a multimeter gives an accurate answer only in 60-70% of cases. The remaining 30% is due to mechanical failures (piston jamming, valve wear), which require disassembling the compressor. But even in this case, the tester will help to isolate electrical faults and narrow down the search for the problem.

1. Preparing for testing: tools and safety precautions

Before you pick up a multimeter, make sure you have everything you need. Minimum set:

• 🔧 Digital multimeter (analog will not work due to low accuracy). It is better with a continuity test function and resistance measurement up to 2000 Ohms.
• 🔌 Phillips/flat head screwdriver for removing the protective cover of the compressor.
• 🧤 Dielectric gloves (rubber with textolite inserts) - required, if you check the breakdown on the case.
• 📝 Paper and pen for recording readings (useful for comparison with standards).

The refrigerator compressor is energized 220-240 V, therefore check should be carried out only on a completely de-energized device. Unplug the refrigerator from the outlet, remove the plug and wait 10-15 minutes - during this time the capacitors of the starting relay will discharge.

⚠️ Attention: If there are traces of oil or oil on the compressor housing rust, clean them with alcohol before checking. Oil can distort the readings when checking for breakdown, and rust can worsen the contact of the probes.

Some models of refrigerators (Beko, Whirlpool) have built-in protection against turning on after a power outage. To reset it, wait 5-7 minutes after unplugging the plug from the socket.

2. Where is the compressor located and how to access its contacts

The compressor (also known as the refrigerator motor) is located at the bottom of the refrigerator, at the back. It is a black or gray metal cylinder with refrigerant pipes and a terminal block. In modern models (Samsung RB30J3000WW, LG GA-B409SLGL), the compressor is often closed with a plastic or metal cover, which is attached to 2-4 self-tapping screws.

To get to the contacts:

1. Unscrew the fastening screws of the cover (usually they are located in the corners).
2. Remove the cover - underneath it you will see a terminal block with 3-4 contacts (depending on the compressor model).
3. Disconnect the wires from the terminals. Remember or photograph their location - incorrect connection after checking can damage the compressor.

On The block usually has contact markings:

• C (Common) - common contact;
• S (Start) - starting winding;
• R (Run) - working winding;
• CS (if any) - contact for protection against overheating.

If there is no marking, focus on the color of the wires (standard for most refrigerators):

• 🔴 Red/orange - starting winding (S);
• 🔵 Blue/black - working winding (R);
• ⚪ White/yellow - general (C).

⚠️ Attention: In refrigerators with a system No Frost (for example, Atlant MXM 2835-90) there may be two compressors - separately for the freezer and refrigerator compartments. Check both if you are not sure which one is faulty.

Disconnect the refrigerator from the mains

Remove the back cover of the compressor

Take a photograph of the location of the wires

Disconnect the wires from the terminal block pads

Clean the contacts from oxidation (if necessary)-->

3. Checking the winding resistance: norms and deviations

The main test is measuring the resistance between the compressor windings. This allows you to identify breaks, short circuits or interturn breakdowns. Connect the multimeter to resistance measurement mode. (Ω) to the limit 2000 Ohm.

Check procedure:

1. Measure the resistance between C and S (starting winding).
   

   Normal: 20-40 Ohm (depending on the model). If the readings tend to infinity (OL) - winding break. If close to zero (0-1 Ohm) - short circuit.

2. Measure the resistance between C and R (working winding).
   

   Norm: 10-20 Ohm. Deviations are the same: OL - open, 0-1 Ohm - short circuit.

3. Measure the resistance between S and R.
   

   It should be equal to the sum of the first two measurements (for example, if C-S = 30 Ohm and C-R = 15 Ohm, then S-R = 45 Ohm). value less - interturn short circuit.

If the resistance does not correspond to the norm:

• 🔧 Breakage (OL) —rewinding of the winding or replacement of the compressor is required.
• ⚡ Short circuit (0-1 Ohm) —often accompanied by a blown fuse in the starting relay. The compressor must be replaced.
• 🔄 Interturn short circuit (resistance S-R less than the amount C-S + C-R) - the compressor will heat up and turn off after 5-10 minutes of operation. The solution is replacement.

4 Check. for breakdown on the housing: why is it critical?

Failure of the winding to the housing is one of the most dangerous faults. It leads to:

• ⚡ Electric shock when touching the refrigerator;
• 🔥 Insulation fire;
• 🛑 Automatic tripping of the RCD (if installed).

To check:

1. Put the multimeter into dial mode (→│) or measure resistance to the limit 2000 kOhm.
2. Connect one probe to any contact of the compressor (C, S or R).
3. Apply the second probe to metal housing of the compressor (after cleaning the paint for reliable contact).

Norm: resistance should tend to infinity (OL). If the readings are less 100 kOhm —there is a breakdown on the body. Such a compressor operation is prohibited needs to be replaced.

⚠️ Attention: In refrigerators with a plastic body (for example, Bosch KAN58A55) breakdown on metal parts (tubes, fastenings) is just as dangerous. Check all metal elements that are accessible without disassembly.

If a breakdown is detected, but the compressor is still working, do not delay repairs. Over time, the insulation will deteriorate and the risk of electric shock will increase. In service centers, such a defect refers to "non-warranty cases" -even if the refrigerator is under warranty, you will have to pay for the repair yourself.

What to do if the multimeter shows a breakdown, but the refrigerator is working?

This is a sign of the initial stage of insulation destruction. The compressor can work from several days to months, but at any moment it is possible:

- Electric shock through the housing;

- Short circuit in the network;

- Failure of the electronic control unit.

We recommend immediately turning off the refrigerator from the mains and replace the compressor.

5. Diagnostics of the starting and protective relay

If the compressor does not start, but the winding resistance is normal, the problem may lie in start relay. It is responsible for starting the engine and protecting against overheating. Most refrigerators use one of three types of relay:

• 🔘 Tablet (PTR) —a round relay with one terminal (used in Indesit, Ardo);
• 🔲 Square (LRI) —with two terminals and a bimetallic plate;
• 🔧 Electronic —in modern models (Samsung, LG with inverter compressors).

Checking the relay:

1. Remove the relay from the compressor (disconnect the wires and unscrew the fasteners).
2. Ring the relay contacts in the mode →│:
   • Between the terminals 2-3 (designations may differ) the resistance should be 0 Ohm - this normally closed contacts.
   • Between 1-2 and 1-3 — OL (open).

If the contacts 2-3 are open (OL), the relay is faulty - requires replacement.

To check protective relay (thermal relay) you will need to heat it. Gently heat its body with a lighter or hairdryer (no higher than 80°C). replacing

6. Additional tests: current consumption and case temperature

If basic tests do not reveal problems, but the compressor is unstable (frequently turns off, does not get cold), perform additional tests.

Measuring current consumption:

• Connect the multimeter to current measurement mode (A~) series with a compressor.
• Normal starting current: 1.2-1.5 A (for household refrigerators).
• Operating current: 0.5-0.8 A.
• If current exceeds 2 A - interturn short circuit or mechanical overload (jamming).

Checking the housing temperature:

• Start the compressor for 10-15 minutes.
• Touch the housing (carefully, it can heat up to 60-70°C).
• Normal: uniform heating to 50-60°CIf one part of the compressor is hot and the other is cold, this is a sign of valve failure or refrigerant leakage.

⚠️ Attention: In inverter compressors (Samsung Digital Inverter, LG Linear Compressor), the current consumption may be lower than standard values (0.3-0.5 AThis is normal - such motors are optimized for energy saving.

If the compressor starts but does not freeze, the problem may not be in it, but in:

• 🧊 Freon leakage (refilling required);
• 🔧 Clogged capillary tube (needs cleaning or replacement);
• 🌡️ Thermostat malfunctions (checked separately).

7. Typical errors during testing and how to avoid them

Even experienced technicians sometimes make mistakes when diagnosing compressor. Here are the most common:

• 🔌 Checking under voltage —this is deadly! Always unplug the refrigerator before starting work.
• 📉 Incorrect measurement limit —if you measure the winding resistance at the limit 200 Ohm, the multimeter may not show the interturn value. short circuit. Use the limit 2000 Ohm.
• 🔍 Ignoring oxidized contacts —oxides distort the readings. Always clean the terminals before checking.
• 🔄 Confusion in the wires —if after checking the wires are incorrectly connected back, the compressor may burn out. Always take photographs of the original connection.
• 🌡️ Diagnostics "for cold" —some faults (for example, insulation breakdown) appear only when the compressor heats up. turns off after 5-10 minutes of operation, check it in a hot state.

Another common error - diagnosis without taking into account the compressor model. For example, for inverter compressors (Panasonic, Hitachi) normal values. resistances may differ by 1.5-2 times from standard ones. Always check the technical documentation for the specific model.

How to find documentation for the compressor?

There is a metal tag with the model on the compressor body (for example, Embraco EGX90HLC or Danfoss NL6L). Enter this model into the search engine with the addition of the word “datasheet” or “technical specifications”. On the first pages you will find official PDFs with standard values.

8. When repair is impossible: signs of compressor “death”

Not all faults. compressors can be repaired. Here are the signs in which only replacement remains:

• 🔥 The winding is burned out - blackened or melted wires, burning smell. Rewinding the winding will cost 70-80% of the cost of a new compressor.
• 🔧 Piston jamming - the compressor is humming. does not start, gets very hot. Often accompanied by a knock when trying to start.
• 💧 Oil leakage - if oil is leaking from the compressor, this is a sign of destruction of the seals or a crack in the housing.
• ⚡ Breakage on the housing - even if the compressor is still running works, it cannot be used.
• 📉 Decreased performance - the compressor works, but does not gain the required pressure (the refrigerator does not freeze). The reason is wear of the valves or piston group.

Cost of a new one. compressor for a household refrigerator - from 5,000 to 15,000 rubles (depending on the model). Replacing the service will cost 2-3 times more. If your refrigerator is more than 10 years old, it is often cheaper to buy a new one than to repair an old one.

The exception is premium models (Liebherr, Miele) with inverter compressors. repairs are justified, since the cost of a new refrigerator starts from 100,000 rubles.

FAQ: Frequently asked questions about checking the compressor. refrigerator

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

Yes, but only the resistance of the windings and breakdown to the housing. To check the current consumption or housing temperature, the compressor must be connected and started, which requires temporary removal of the relays and wires. If you are not confident in your skills, it is better not to risk it and call a specialist.

The multimeter shows the winding resistance is normal, but the compressor does not start. What's the matter?

There may be several reasons:

• The starting relay is faulty (check it separately).
• The starting capacitor has failed (if your model has one).
• Problems in the control unit (for refrigerators with electronic control).
• Mechanical blocking of the compressor (jamming).

Start by checking the relay and capacitor - these are the most common “culprits”.

How to distinguish a compressor malfunction from a freon leak?

If there is a freon leak The compressor works, but the refrigerator does not freeze. In this case:

• The compressor can work without stopping or turn off due to overheating.
• The condenser (grid at the back of the refrigerator) remains cold.
• The tube going from the compressor to the condenser does not heat up.

If the compressor does not start at all, the problem is in it or in the electrical circuit.

Is it possible to repair the compressor yourself (rewinding, replacing valves)?

Theoretically, yes, but in practice this is impractical. Rewinding windings requires special equipment and skills, and the cost of the work will exceed the price of a new compressor. Replacing valves is only possible in a workshop using a vacuum pump and a freon cylinder. This is too complicated and dangerous for home repairs.

Which multimeter is best to use for testing?

Any digital multimeter with resistance measurement accuracy no worse than ±1 Ohmwill do. Popular models:

• DT-830B —a budget option (accuracy is enough for diagnostics).
• Mastech MS8268 —a professional device with automatic range adjustment.
• Fluke 17B —premium class, high accuracy and reliability.

Analog (arrow) multimeters are not recommended due to low accuracy at low resistances.