When the refrigerator suddenly stops freezing, the first suspect becomes the compressor - the “heart” of the system, responsible for circulating the refrigerant. But before you take the equipment to a service center or buy a new unit, you should make sure that the problem is in it. Multimeter is an affordable tool that will help diagnose the problem in 15–20 minutes without disassembling the refrigerator.
In this article you will find unique standard resistance values for compressors of different brands (including rare models), detailed diagrams for connecting the probes, as well as an algorithm for checking for open circuit, interturn short circuit and breakdown to the housing. We will look at how to distinguish a “dead” compressor from a working one, even if it looks intact on the outside, and what to do if the multimeter readings do not fit into the standard ranges.
Important: diagnostics require accuracy. Errors in measurements can lead to false conclusions or, in the worst case, damage to the refrigerator's electronics. If you have never worked with electrical appliances, it is better to invite a specialist - but for experienced users, this instruction will become a reliable guide.
1. Preparing for diagnostics: tools and safety measures
Before checking the compressor, make sure that you have everything you need:
- 🔧 Multimeter (digital or analogue) with resistance (Ω) and continuity measurement modes. Even a budget model like DT-830B.
- 🔌 Screwdriver (cross or flat - depends on the fastenings on the back panel of the refrigerator) is suitable.
- 📏 Pliers or pliers for removing terminals (if they are clamped too tightly).
- 📝 Notepad to record readings - this will help compare them with reference values later.
Safety comes first. The compressor operates under voltage 220–240 Vtherefore:
⚠️ Attention: Before starting work required unplug the refrigerator and wait until the capacitor is discharged (5-10 minutes). Touching the compressor terminals while the power is on is deadly!
If your refrigerator is equipped with an electronic control unit (as in models Samsung No Frost or LG Inverter), before diagnostics, disconnect it from the compressor. Otherwise, the multimeter readings may be distorted.
2. Where is the compressor located and how to get to it
The compressor is usually located at the bottom of the refrigerator, at the back. It looks like a black or gray oval tank with pipes and a terminal block. In modern models (for example, Bosch KGE39XW25R or Liebherr CNef 4315), the compressor may be hidden under a decorative panel - it will have to be removed.
Access algorithm:
- Unplug the refrigerator from the outlet.
- Move it away from the wall (minimum distance is 50 cm for convenience).
- Remove the back protective cover by unscrewing the screws (usually 4-6 pieces).
- Find the compressor - it is connected to the start relay (small box with wires).
On the compressor terminal block you will see three terminals, marked with letters:
S(Start) - starting winding;R(Run) - working winding;C(Common) - common terminal.
Sometimes the markings may differ (for example, M, P, T on old Soviet refrigerators). If there are no letters, focus on the location: the common terminal is usually located in the middle.
How to distinguish a compressor from a condenser?
A compressor is an oval tank with tubes and terminals, and a condenser is a grid of tubes (usually black or gray) located at the back or on the sides refrigerator. The condenser heats up during operation, the compressor vibrates and makes a hum.
3. Checking the resistance of the compressor windings
This is a key test that will show whether the windings are working properly. Connect the multimeter in resistance measurement mode (Ω) to the compressor terminals in the following sequence:
| Measured terminals | Normal resistance (Ohm) | What does deviation mean |
|---|---|---|
C → R (general → working) |
15–40 Ohm | More than 40 Ohm - winding break; less than 15 Ohm - interturn short circuit. |
C → S (common → starting) |
20–50 Ohm | Readings out of range - faulty starting winding. |
R → S (working → starting) |
Sum C→R + C→S (35–90 Ohm) |
If the value is not equal to the sum of the first two - open or short circuit. |
Example: if during measurement C→R the multimeter showed 25 Ohms, and C→S - 35 Ohms, then R→S should be 60 Ohms. If there are 120 Ohms or 0, the windings are faulty.
⚠️ Attention: In inverter compressors (for example, in refrigerators Panasonic NR-BN or Hitachi R-WB) the resistance of the windings can be higher - up to 150 Ohms. Check the data for your model!
If at least one measurement shows 0 Ohm (short circuit) or ∞ (open circuit), the compressor must be replaced. Also pay attention to:
- 🔥 Blackened terminals - a sign of overheating or burnt contacts.
- 💧 Oil traces around the compressor - a possible refrigerant leak.
- 🔊 Extraordinary sounds when turned on (clicking, grinding) - mechanical failure.
Measure resistance C→R (15–40 Ohm)|
Measure resistance C→S (20–50 Ohm)|
Check the sum of R→S (should be equal to C→R + C→S)|
Inspect the terminals for burning or melting -->
4. Testing for breakdown to the housing (short to ground)
This test determines whether the compressor is “breaking through” the metal body of the refrigerator. If this happens, when you touch the refrigerator, it may give you an electric shock, and the machine in the panel may knock it out.
How to check:
- Put the multimeter in dial mode (diode or buzzer icon).
- Connect one probe to any terminal compressor (
C,RorS). - Attach the second probe to metal case the compressor (not to the paint!).
If the multimeter shows 0 Ohm or emits a beep, the compressor is broken. Normally, the resistance should tend to ∞ (infinity).
If a breakdown occurs, the compressor is subject to It cannot be replaced - it cannot be repaired. You cannot put the refrigerator into temporary operation: it is dangerous for life!
5. Diagnostics of the starting and protective relay
If the compressor is working, but the refrigerator does not work, the problem may lie in starting relay (starts the compressor) or protective relay (turns off when overheated). These parts often fail due to voltage surges or wear.
How to check the relay:
- 🔍 External inspection: Remove the relay from the compressor and check for cracks, melts or traces of burnt plastic.
- 📏 Contact testing: in normal condition, the contacts
3–4(on the relay diagram) should ring, and1–2—no. When shaking, the relay should not rattle (a sign of a broken spring). - 🔋 Checking the coil: relay winding resistance should be within the limits
50–200 Ohm.
If the relay is faulty, it can be replaced separately - this is cheaper than buying a new compressor. For models Atlant and Stinol a universal relay is suitable RTK-X, for LG and Samsung — original parts marked 6701A or RLS-8.
6. Common mistakes when checking and how to avoid them
Even experienced professionals sometimes make mistakes that lead to incorrect conclusions. Here's what you shouldn't do:
- ❌ Measure resistance with the power connected. This is not only dangerous, but also distorts the readings.
- ❌ Ignore the compressor temperature. If it is hot, the resistance of the windings may temporarily increase. Let it cool for 1-2 hours.
- ❌ Confuse the terminals
RandS. This will lead to incorrect interpretation of the readings. Always check the diagram! - ❌ Neglect checking the relay. In 30% of cases, “symptoms of a dying compressor” are caused by a faulty relay.
If you doubt the results, repeat the measurements 2-3 times or compare the readings with the reference ones for your model. For example, for compressors Danfoss (installed in Electrolux and AEG) normal resistance C→R — 20–25 Ohm, and for Secop (former Danfoss) — 12–18 Ohm.
7. What to do if the compressor is faulty
If diagnostics show that the compressor has failed, you have three options:
- Replacing the compressor. New original compressor for refrigerators Atlant or Biryusa will cost
8 000–15 000 ₽, for LG/Samsung —15 000–25 000 ₽. The work of the master is also3 000–6 000 ₽. - Compressor repair. In some cases (for example, when the shaft is jammed), it is possible to restore functionality by changing the oil or cleaning. temporary solution - the service life of a repaired compressor rarely exceeds 1–2 years.
- Purchasing a new refrigerator. If your equipment is more than 10 years old, replacing the compressor may not be cost-effective. Modern models (for example, Indesit ITS 5180 W or BEKO GNE114620X) consume 30–40% less electricity.
Before purchasing a new compressor, make sure that it is compatible with your refrigerator model. Basic parameters for selection:
- 🔹 Refrigerant type (
R134a,R600a,R290). - 🔹 Power (for example,
120 Wfor small cameras,200 Wfor large ones). - 🔹 Mounting type (flange or suspended).
⚠️ Attention: When replacing a compressor, be sure to replace filter drier and fill the system with new refrigerant, otherwise the new compressor will quickly fail due to contamination in the system.
FAQ: Answers to frequently asked questions
Is it possible to check the compressor without removing it from the refrigerator?
Yes, but only if you disconnect all the wires from the terminal block. Checking "in weight" without disconnecting the wires. will give incorrect results due to parallel circuits (relay, thermostat). Also make sure that the refrigerator is disconnected from the network!
What resistance should the refrigerator compressor have? data-i="236">or Indesit?
For most models Indesit (For example, C132G or T18AA) normal values:
C→R:25–35 Ohm;C→S:30–40 Ohm;R→S:55–75 Ohm.
Deviation by ±10% is acceptable, but if the difference is greater, the compressor is faulty.
Why does the compressor hum but does not start?
This is a typical symptom of a faulty start relay or capacitorAlso the cause may be:
- Interturn short circuit in the winding
S(starting). - Jamming of the compressor shaft (you need to check whether it rotates manually when power off).
- Low voltage in the network (less than
190 V).
Check the relay and voltage in the socket with a multimeter.
Is it possible to turn on a refrigerator with a faulty compressor?
Absolutely not! If the compressor has a breakdown in the housing, it is life-threatening. If the windings are shorted or broken, the refrigerator will not work, and repeated attempts to start can lead to fire of the wiring or failure of the electronic unit.
How much does it cost to diagnose a compressor in a service center?
In official services (Atlant-Service, LG Service) diagnostics will cost 1 500–3 000 ₽. Private repairmen charge 1 000–2 000 ₽. However, if you have already checked with a multimeter, you can save money and immediately take the refrigerator for repair with a clear description of the fault.