Checking the windings of the refrigerator compressor: a detailed guide with tables and diagrams

When the refrigerator suddenly stops freezing, and the motor-compressor does not start or works intermittently, the first thought is a breakdown of the electric motor. But before taking the equipment to a service center or buying a new compressor, you should check its windings yourself. Testing the windings with a multimeter allows you to identify breaks, interturn short circuits or breakdowns in the housing - the three main faults that make repairs unprofitable.

This procedure does not require professional equipment: it is enough a conventional tester (multimeter) with resistance measurement mode. However, without knowledge of the connection diagram and standard resistance values ​​for different types of compressors (Danfoss, Embraco, Secop etc.), it is easy to make a mistake. In this article we will analyze unique signs of winding malfunction that are not described in standard instructionsand also provide a diagnostic checklist taking into account the features of modern inverter and linear compressors.

Why it is important to check the compressor windings

The compressor is the “heart” of the refrigerator, and its windings operate under extreme conditions: high temperatures, vibrations, voltage surges. Even a microcrack in the insulation or overheating from poor cooling can lead to:

• 🔥 Interturn short circuit - the most common problem in which the winding resistance drops below normal and the current consumption increases. This leads to overheating and operation of thermal relay.
• ⚡ Breakdown to the body - a dangerous malfunction in which current “leaks” to the metal body of the compressor. In the best case, the RCD will work, in the worst case, it will give you an electric shock.
• 🔌 Winding break - complete lack of contact when the multimeter shows infinite resistance. The compressor is silent and does not respond to the starting relay.

Without diagnostics, you risk replacing a working starting relay or thermostat, wasting time and money. For example, Embraco EG series compressors often suffer from interturn short circuits due to thin insulation, and Danfoss NL - breakdowns to the housing after 10 years of operation. Knowing these features, you can more accurately determine the cause.

Preparing for the call: tools and safety measures

Before touching the compressor, be sure to disconnect the refrigerator from the mains discharge the capacitors (if they are in the circuit). To work you will need:

• 🔧 Multimeter with an ohmmeter (200 Ohm range) and a megaohmmeter (to check insulation) mode. Even a budget model is suitable DT-830B.
• 🔨 A screwdriver or wrench for removing the start relay (if it is removable).
• 📝 Connection diagram of your compressor (usually pasted on the case or in the instructions for the refrigerator).
• 🧤 Dielectric gloves (optional, but recommended when checking breakdown on the housing).

Important: if the compressor is hot, let it cool for 30-40 minutes. Testing the heated windings will give incorrect readings due to the change copper resistance. Also check whether the thermal relay has tripped - sometimes it is enough to “reset” it with a button on the housing.

⚠️ Attention: If traces of melting, blackening are visible on the compressor housing, or a burning smell is felt, further diagnostics are dangerous! There is a high risk of a short circuit when voltage is applied.

Connection diagram of the compressor windings: where are they? contacts

Most household compressors have three terminals, marked with letters:

• S (Start) - starting winding. It has the highest resistance (usually 20–40 Ohms).
• R (Run) - working winding. Resistance 10–20 Ohm.
• C (Common) - general conclusion. The resistance between C and S/R must correspond to the sum of the resistances of the windings.

If there is no marking, do not panic: the windings can be identified by their resistance. The working winding always has less resistancethan the starting one. For example, a compressor Embraco EG80HLC typical values: R–C = 15 Ohm, S–C = 30 Ohm, S–R = 45 Ohm (sum of the first two).

U inverter compressors (for example, LG LW24 or Samsung Digital Inverter) resistance is lower due to the control features. If your values ​​differ greatly from the table ones, this is a cause for concern.

What if there are 4 outputs on the compressor?

The fourth output is usually thermal protection or a temperature sensor. To test the windings, use the three main contacts (S, R, C), ignoring the fourth. If in doubt, check the markings on the compressor nameplate.

Step-by-step instructions: how to test the windings with a multimeter

The testing algorithm is the same for all types of compressors, but there are nuances for inverter models. Follow the steps:

1. Step 1. Removing the start relay.

   Disconnect the relay from the compressor (usually it is secured with latches or screws). If the relay is non-removable (like some Secop), call directly through its contacts, but take into account the resistance of the relay coil (usually 5-10 Ohms).

2. Step 2. Check the resistance of the windings.

   Set the multimeter to ohmmeter mode (200 Ohms). Measure the resistance between pairs of contacts one by one:

   • R–C (working winding) → should be 10–20 Ohms.
   • S–C (starting winding) → should be 2 times greater than R–C.
   • S–R → sum R–C i S–C.

Step 3. Check for breakdown of the housing.

Switch the multimeter to megohmmeter mode (20 MOhm). Touch each terminal (S, R, C) with one probe in turn, and the metal body of the compressor with the second. The resistance should be infinite (OL). Any value below 10 MOhm is a sign of breakdown.

Step 4. Checking the interturn short circuit.

It is impossible to accurately diagnose an interturn short circuit with a multimeter, but an indirect sign is winding resistance is below normal by 20% or more. For example, if for your model R–C there should be 15 Ohms, and the multimeter shows 10 Ohms, there is a high risk of interturn.

If all values are normal, but the compressor does not start, the problem may be in start relay, thermostat or electronics. For inverter compressors, also check the control board - it often fails during voltage surges.

Decoding the results: what do the multimeter readings mean

The data must be interpreted taking into account the compressor model and its condition. Below are typical scenarios:

Critical nuance: if the compressor It hums, but does not start, and the winding resistance is normal, the starting relay or capacitor is to blame. In 80% of cases, replacing the relay (cost ~500–1500 rubles) solves the problem without purchasing a new compressor.

⚠️ Attention: If the compressor was previously repaired (for example, the leads were soldered), the winding resistances may differ from the table ones by 10–15%. In this case, focus on the symmetry of the values ​​between the windings.

Frequent errors when dialing and how to avoid them

Even experienced technicians sometimes make mistakes that lead to an incorrect diagnosis. Here are the most common ones:

• 🔌 Continuity under voltage. Never measure resistance without disconnecting the compressor from the mains! This is not only dangerous, but also distorts the readings.
• 🌡️ Ignoring the compressor temperature. Hot windings have a resistance 10–15% higher than cold ones. Always cool the compressor before checking.
• 🔍 Confusion with contacts. If you confuse S and R, you can mistakenly diagnose an interturn short circuit. Always check the diagram!
• 📉 Not taking into account the resistance of the wires. When measuring the resistance of the windings through the starting relay, add to the result the resistance of its coil (usually 5-10 Ohms).

Another typical mistake is checking only the windings without testing for breakdown of the case. The breakdown may not appear immediately, but it is life-threatening! Always ring all three terminals on the case.

What to do if the windings are faulty: repair or replacement?

Unfortunately the compressor windings are not repaired. Rewinding at home is impossible due to the difficulty of insulating and balancing the rotor. The only options:

• 🔄 Replacement of the compressor. A new compressor costs from 5,000 to 20,000 rubles. depending on the model. For refrigerators older than 10 years, replacement is often unprofitable.
• 🛠️ Replacement of the refrigerator. If the cost of the compressor exceeds 30–40% of the price of new equipment, it is more advisable to buy a new refrigerator.
• 🔧 Purchasing a used compressor. Risky option — a used compressor can last from a week to a year. Check its resistance before purchasing!

Exception - breakdown to the housing. Sometimes it can be eliminated by insulating the compressor housing with a special resin (for example Epoxylin). However, this is a temporary solution, and such a compressor cannot be operated without grounding.

Before purchasing a new compressor, make sure that:

• The new model is compatible with type of refrigerant (R134a, R600a, etc.).
• Power and performance are not lower than the old one.
• Dimensions allow you to install the compressor in the old place.

⚠️ Attention: When replacing a compressor, be sure to replace filter drier and evacuate the system before charging with refrigerant. Otherwise, moisture and debris will quickly damage the new compressor.

FAQ: Frequently asked questions about checking the compressor

Is it possible to check the compressor without removing the starting relay?

Yes, but the readings will be less accurate due to the resistance of the relay coil. For accurate diagnostics, it is better to remove the relay. If the relay is non-removable, subtract its resistance (usually 5-10 Ohms) from the obtained values.

What insulation resistance is considered normal?

For household compressors, the insulation resistance (between the terminals and the housing) should be at least 10 MOhm. If the multimeter shows less than 2 MOhm, the compressor is unsafe and must be replaced.

Why does the compressor hum but does not start, although the windings are working?

The reasons may be:

• Faulty starting relay or capacitor.
• A jammed rotor (try to manually turn the shaft through the pulley).
• Low voltage in the network (less than 190 B).
• Faulty control board (for inverter models).

How to check an inverter compressor?

Inverter compressors (LG, Samsung, Hitachi) ring in the same way, but they have lower winding resistance (usually 5–15 Om). Also check the inverter board for burnt elements (blackened resistors, swollen capacitors).

Is it possible to repair the interturn short circuit?

No. An interturn short circuit can only be eliminated by rewinding the windings at the factory, which costs more than a new compressor. This is impossible at home.