Check refrigerator compressor with a multimeter: a detailed guide with photos and diagrams

The compressor is the “heart” of the refrigerator, and its failure leads to complete failure of the equipment. If the unit does not freeze, makes strange sounds, or constantly works without stopping, the first thing you need to do is check the serviceability of the motor-compressor. You can do this yourself using a regular one multimeter, without resorting to the services of a specialist. In this article, we will look at how to correctly ring the windings, measure resistance and current, and also identify typical faults - from interturn short circuits to breakdowns on the housing.

It is important to understand that diagnostics require accuracy: work is carried out with electricity, and errors in measurements can lead to false conclusions. We will describe in detail each stage - from preparing tools to analyzing the results - taking into account the features of different compressor models (Danfoss, Embraco, Secop etc.). You will also find out which indicators are considered normal and which indicate the need to replace the part.

If you have never held a multimeter in your hands, do not worry: the instructions are adapted for beginners. We will explain what settings to set on the device, how to connect the probes and what the numbers on the screen mean. And for experienced craftsmen, we will provide extended testing schemes, including tests under load and diagnostics of the starting relay.

Preparing for testing: tools and safety measures

Before you begin diagnostics, make sure that you have everything you need. Minimum set of tools:

• 🔧 Multimeter (digital or analog) with resistance (Ω) and voltage (V) measurement modes. Even a budget model like DT-830B.
• 🔌 Phillips/flathead screwdriver for removing the compressor protective casing is suitable.
• 🧲 Pliers or wire cutters for working with terminals (if you need to disconnect wires).
• 📏 Insulating tape or heat shrink tube to isolate the contacts after checking.

Be sure to unplug the refrigerator 10-15 minutes before starting work. This is necessary not only for safety, but also to ensure that the capacitors in the circuit are discharged. The compressor is located at the bottom of the refrigerator, usually covered with a metal lid or plastic casing. In some models (Samsung No Frost, LG Inverter), access to it may be difficult - you will need to remove the back panel.

⚠️ Attention: If traces of oil, melted plastic or burning are visible on the compressor housing or near it - do not touch the part with your bare hands and do not turn on the refrigerator until you replace the compressor. These are signs of a short circuit that can lead to a fire.

Before disassembling the refrigerator, take a photograph of the location of all wires and terminals on the compressor. This will help avoid errors during reassembly. If you are working with an inverter compressor (Panasonic, Hitachi), please note that its electronic control unit is sensitive to static electricity - touch the boards only with a grounded tool.

Compressor connection diagram: where and what call

To properly check the compressor, you need to understand its structure. In classic models (not inverter), the motor has three outputs:

• 🔹 Common (Common, C) — connected to the compressor housing.
• 🔹 Working winding (Run, R) —the main winding, works constantly.
• 🔹 Start winding (Start, S) - turns on only at startup.

In inverter compressors, the circuit is more complicated: there can be up to 5-6 pins, and control is carried out through an electronic module. If your refrigerator is equipped with an inverter (Samsung Digital Inverter, LG Linear Compressor), for diagnostics you will need a diagram of a specific model - there are no universal solutions.

The following is a typical connection diagram for a conventional compressor:

In practice, conclusions can be labeled in different ways. For example, in compressors Embraco the designation M (Main) is often used instead of C, and in Danfoss — P (Permanent) for the working winding. If there are no markings, you will have to determine the terminals using the wiring method (more on this below).

Testing compressor windings: step-by-step instructions

Now let's move on to the practical part. Follow this algorithm:

1. Remove the terminals from the compressor terminals. If the wires are soldered, carefully disconnect them with pliers, remembering the location.
2. Switch the multimeter to resistance measurement mode (Ω) to the range 200 Ohm.
3. Ring pairs of pins:
   • 🔹 C → R (common + working winding)
   • 🔹 C → S (common + starting winding)
   • 🔹 R → S (working + starting winding)

Record the readings and compare them with the standards from the table above.

Check the insulation: one multimeter probe to any terminal, the second to the compressor housing. The resistance should tend to infinity (OL).

Consider the possible results:

• ✅ All three measurements (C-R, C-S, R-S) show final values —the windings are intact, but you need to check their resistance.
• ❌ Any measurement shows 0 Ohm —short circuit in the winding.
• ❌ Any measurement shows OL (open) —break in the winding.
• ❌ The resistance between the terminal and the housing is not OL —breakdown to the housing (dangerous!).

If you find a short circuit or breakdown, the compressor must be replaced. If the winding breaks, rewinding sometimes helps, but at home this is unrealistic - special equipment is required.

Disconnect the refrigerator from the network forever|Do not touch the compressor housing|Call a technician to replace the part|Do not turn on the refrigerator until the fault is eliminated-->

Checking the resistance of the windings: norms and deviations

Winding resistance is a key parameter that indicates the condition of the compressor. For most household refrigerators (Atlant, Indesit, Beko), the following standards apply:

• 📊 Working winding (C-R): 10–30 Ohm. If the value is below 10 Ohms, an interturn breakdown is possible, if above 30 Ohms, the winding is “burnt.”
• 📊 Starting winding (C-S): 15–40 Ohms. Deviations indicate aging of the insulation or overheating.
• 📊 Total resistance (R-S): must be equal to the sum of C-R and C-S (an error of ±5 Ohms is allowed).

For example, if during measurement C-R you received 12 Ohms, and C-S - 20 Ohms, then R-S should be about 32 ohms. If the actual value is very different (for example, 50 Ohms), this indicates a malfunction.

In inverter compressors, the winding resistance is usually lower - 5–15 Ohms for working and 8–25 Ohms for starting. This is due to the features of their design. If you diagnose LG Inverter Linear Compressor, be guided by the data from the service manual of a specific model.

⚠️ Attention: If the resistance of the starting winding (C-S) is zero, but C-R is normal, the problem may be in starting relay. Check it separately (more on this in the next section).

Also pay attention to resistance difference between the windings. If, for example, C-R = 10 Ohm, and C-S = 50 Ohm, this is abnormal - most likely, there is a break in some of the turns in the starting winding. Such a compressor will start with difficulty or will not start at all.

Why can the resistance of the windings change over time?

The resistance depends on the temperature of the copper: when heated, it increases. If the compressor operated in overload mode for a long time (for example, due to a freon leak or high room temperature), the windings could “burn out.” Moisture inside the housing also affects the resistance - it leads to corrosion and an increase in contact resistance.

Diagnostics of starting and protective relays

If the compressor does not start, but the windings are ringing normally, the problem may lie in start relay. This device temporarily connects the starting winding at the moment of start, and then disconnects it. Modern refrigerators (Samsung, Liebherr) often use a combination relay, which also serves as a overheat protection.

To check the relay:

1. Remove it from the compressor (usually mounted on the motor housing).
2. Ring the contacts:
   • 🔹 Between the terminals C and R the resistance should be equal to the resistance of the working winding.
   • 🔹 Between C and S in normal condition - OL (open).

Apply 220V voltage to the relay (via an extension cord with a plug) and check if the contacts C-S for 1-2 seconds when turned on.

If the relay does not work or the contacts are burnt, it needs to be replaced. The cost of a new part is from 500 to 2000 rubles, depending on the model. For refrigerators Atlant and Biryusa universal relays such as RTK-X are suitable or DANFOSS 103N0010.

Also check thermal protection relay (if it is placed separately). It should open the circuit at temperatures above 120–140°C. To check, heat the relay with a hairdryer and ring the contacts - they should open.

Checking the compressor current under load

If the static test did not reveal any problems, but the refrigerator still does not work, you need to measure starting and operating current the compressor. This is a more complex procedure, as it requires voltage supply.

Sequence of actions:

1. Connect the compressor to the network via current clamps or a multimeter in current measurement mode (A). Set the limit 10 A.
2. Start the compressor. In the first 1–2 seconds, the current can reach 8–12 A (starting current), then it should drop to 0.8–1.5 A (operating current).
3. If the current does not drop or the compressor turns off after a few seconds, the problem is in the mechanical part (jamming, piston failure).

Normal current values depend on the compressor model:

• 🔋 Compressors Danfoss (for example, NL/NM series): starting up to 10 A, operating 0.9–1.3 A.
• 🔋 Compressors Embraco (for example, EG/NE series): starting up to 8 A, operating 0.7–1.2 A.
• 🔋 Inverter compressors: current smoothly changes in the range of 0.5–2 A.

⚠️ Attention: Measuring current under load is a dangerous procedure. If you are not confident in your skills, it is better to entrust it to a professional. A short circuit if connected incorrectly can damage not only the compressor, but also the electrical wiring.

If the current is significantly higher than normal, this may indicate:

• 🔹 Interturn short circuit in the windings (even if it is not detected).
• 🔹 Compressor shaft jamming (disassembly and lubrication required).
• 🔹 Increased pressure in the system (for example, due to a clogged capillary tube).

Typical compressor malfunctions and their symptoms

Based on the test results, you can diagnose specific problems. Here are the most common malfunctions and their symptoms:

If the compressor starts, but the refrigerator does not freeze, the problem may not be in it, and in freon leakage, clogging of the capillary tube or thermostat malfunction. In this case, a more in-depth diagnosis will be required using a manometric manifold.

For refrigerators with the system No Frost (Samsung, LG, Bosch) there is another problem - evaporator freezing, due to which the compressor works without stopping. Before checking the compressor, make sure that the evaporator fan is rotating and the defrost heating element is working properly.

What to do if the compressor is faulty?

If diagnostics showed that the compressor is faulty, you have three option:

1. Replacing the compressor —the most reliable, but expensive method. A new compressor for refrigerators Atlant or Stinol will cost 5,000–12,000 rubles, plus the cost of refilling with freon (1,500–3,000 rubles).
2. Compressor repair is only possible in case of mechanical faults (for example, replacing the oil seal or cleaning valves). The windings are not rewound at home.
3. Purchase of a new refrigerator —it is advisable if the age of the equipment is more than 10 years or the cost of repair exceeds 50% of the price of a new unit.

When replacing the compressor consider:

• 🔧 The new compressor must be the same model or fully compatible in terms of power, type of freon and oil.
• 🔧 After replacement, be sure to vacuum the system (remove moisture and air) and fill with fresh freon.
• 🔧 If the compressor was changed due to an interturn short circuit, check starting relay and capacitor - they could have suffered from a surge current.

For refrigerators with inverter compressors (LG, Samsung), repairs are more expensive due to the complexity of the electronic control unit. In some cases, it is cheaper to buy a new refrigerator than to restore an old one.

FAQ: Frequently asked questions about checking the compressor

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

Yes, but only partially. You can ring the windings and measure the resistance without dismantling, but to check the current under load or diagnose the mechanical part (for example, a jammed shaft), the compressor will have to be removed. Also note that in some models (Samsung with a lower motor) access to the terminals is difficult - you will need to remove the back panel.

What resistance should be between the starting and working windings (R-S)?

Resistance between R and S should be equal to the sum of the resistances C-R and C-S (with an error of ±5 Ohms). For example, if C-R = 15 Ohm, and C-S = 25 Ohm, then R-S should be about 40 Ohm. If the value is very different, this indicates a malfunction of one of the windings.

What to do if the compressor hums but does not start?

In 90% of cases, the problem is in the starting relay or capacitor. Try replacing the relay with a known good one (you can temporarily take it from another refrigerator). If this does not help, check the capacitor: its capacity should correspond to the nominal value (usually 10–40 µF). Also make sure that the compressor shaft rotates freely - sometimes it jams due to lack of oil or dirt.

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

At home - no. Rewinding windings requires special equipment, skills and knowledge of wire parameters (diameter, number of turns, insulation). Even in service centers, such repairs are practically not performed due to the high labor intensity and cost. It is much easier and cheaper to replace the compressor with a new one.

How to check an inverter compressor?

Inverter compressors (LG Linear Compressor, Samsung Digital Inverter) are checked according to the same principle, but taking into account the features:

• 🔹 Resistance windings are usually lower (5–15 Ohms).
• 🔹 The starting relay is integrated into the electronic unit, which also needs to be diagnosed.
• 🔹 For an accurate check, an oscilloscope is required (checking signals from the control unit).

If you are not confident in your skills, it is better to contact a service center — errors in diagnosing inverter systems can lead to failure of the electronic module.