The situation when the refrigerator stops freezing, and there is silence inside or only a quiet hum is heard without starting the engine, always takes you by surprise. It is at such moments that the owner is faced with the question of how to ring the compressor of a home refrigerator in order to understand whether the motor is alive or will have to be changed. Diagnostics the starting-protective device and the electric motor itself is the first and most important step to avoid buying expensive equipment or, conversely, an unnecessary call to the technician.
The compressor is the heart of the refrigeration system, and its failure is often confused with failures of other components, such as a thermostat or start relay. Before proceeding with complex measurements, it is necessary to visually assess the condition of the device and make sure that there is voltage in the network. Electric motor A refrigerator is a fairly reliable device, but is subject to high loads, overheating and voltage surges, which can lead to internal damage to the windings.
In this article we will examine in detail process diagnosis with a multimeter, we will explain how to interpret the readings of the device, and consider typical malfunctions. You will learn to distinguish an open circuit from an interturn short circuit and understand when repairs make sense and when the compressor can no longer be saved. The correct one Initial visual assessment and preparation for diagnosis will save you time and money, allowing you to make an informed decision on further actions.
Initial visual assessment and preparation for diagnosis
Before taking hands and measuring instruments, it is necessary to conduct a thorough visual inspection and preparation of the workplace. Safety is priority number one, since we will be working with electricity and high voltage components. Make sure that the refrigerator is completely disconnected from the electrical outlet, the cord is unplugged, and access to the rear wall is provided.
Remove the protective cover at the bottom of the unit where the compressor is located. Carefully inspect the wires going to the start-protective relay and the engine itself. There should be no melted insulation, blackening or obvious signs of short circuit. If you see that the wires have melted or blackened, this may indicate overheating contacts or a malfunction in the electrical circuit.
⚠️ Attention: If traces of oil are visible on the compressor housing or wires, this may indicate mechanical damage or depressurization of the system. In this case, electrical continuity may be secondary, since freon leakage makes the refrigerator impossible to operate.
Clean the contacts from dust and dirt, as oxidation can distort instrument readings. For diagnostics, you will need a multimeter (tester), a screwdriver to remove the relay cover, and possibly pliers. Make sure that your multimeter is in good working order: the batteries are not discharged, and the probes have complete insulation.
☑️ Preparing to check the compressor
Removing the starting relay and access to the contacts
To ring the compressor windings, you need to gain direct access to the motor contact terminals. To do this, you need to remove the start relay, which is usually mounted on the side or top of the compressor. Carefully remove the plastic casing of the relay, having previously noted or photographed its position, since incorrect installation can lead to breakdown.
After removing the protective casing, disconnect the relay from the contact group of the compressor. Usually it is simply slipped onto the three motor output pins. Be careful not to use excessive force to avoid breaking the plastic clips or damaging the fragile contacts. At this stage, you can already carry out an initial inspection of the relay itself for a burning smell or cracks.
Now three contacts of the compressor, arranged in a triangle, are open in front of you. These are the conclusions of the windings: starting, working and general wire. It is between these contacts that we have to carry out resistance measurements. It is important not to confuse their purpose, although for the initial continuity testing of the windings the strict sequence is not yet critical.
If the contacts are oxidized, they can be carefully cleaned with fine sandpaper or a file, but be careful not to completely grind off the metal. Clean contact is the key to accurate readings from the device. After preparation, you can proceed directly to measurements.
Setting up a multimeter and searching for a winding diagram
For correct diagnostics, you must correctly configure the measuring device. Switch the multimeter to resistance measurement mode (indicated by the Ω or ohm symbol). Select a measurement limit of 200 Ohms or 2 kOhms, since the winding resistance of household compressors is usually in the range from 10 to 100 Ohms.
Before measuring the compressor, check the multimeter itself by shorting the probes to each other. The device should show zero or a value close to zero (resistance of the probe wires). If the device shows one or infinity with the probes closed, it means that it is faulty or the battery is dead.
Now you need to determine which contact is which. Usually the terminals are marked with letters on the case or in the documentation, but often the markings are erased or missing. In the standard circuit:
- 🔹 Common wire (C or S) — often located separately or on top of the triangle.
- 🔹 Start winding (S or Start) —has a higher resistance.
- 🔹 Working winding (R or Run) —has a lower resistance.
To avoid confusion, remember a simple rule: the resistance between the working and starting windings is equal to the sum of the resistances of each of them relative to the common wire. That is, if you find two contacts with the least resistance between them, the third contact that remains “overboard” will be common.
How to determine the common wire without a circuit
Measure the resistance between all three pairs of contacts. The pair with the highest resistance is the start and run windings together. The third contact, not participating in this pair, is the common one. From it to the working one there will be the least resistance, and to the starting one there will be an average one.
The process of testing the windings: step-by-step instructions
We begin the direct testing. Touch the multimeter probes to any two contacts. Record your readings. Then move the probes to another pair of contacts. In total you will have three measurements between three contacts. Normal resistance values for a working compressor vary, but are usually:
The resistance between the common and working contacts should be in the range of 10–30 Ohms. The resistance between the common and start contacts is usually higher - from 30 to 100 Ohms. The sum of these two values should approximately equal the resistance between the working and starting contacts. If you see such values, it means winding integrity the integrity of the windings is not broken.
It is important to pay attention not only to the numbers, but also to the stability of the readings. If the numbers on the multimeter screen “jump” or increase slowly, this may indicate poor contact between the probes or the presence of moisture inside the engine. In the latter case, the compressor may require drying, but more often this is a sign of more serious problems.
| Measurement type | Normal value | What does deviation mean |
|---|---|---|
| General - Working | 10–30 Ohm | Open or short circuit |
| General - Starting | 30–100 Ohm | Open or short circuit |
| Worker - Starter | The sum of the two is higher | Scheme violation |
| Any contact - Housing | Infinity (1) | Breakdown on the body |
If the multimeter shows one (infinity) when testing a pair of contacts, this means break circuits. In this case, the engine will not work. If the device shows zero or a value close to zero (1-2 Ohms), this is a sign short circuit turns, which is also fatal for the motor.
Diagnostics of a breakdown on the case (interturn short circuit)
One of the most dangerous faults is a breakdown of the winding insulation on the compressor housing. This can lead not only to equipment failure, but also to electric shock when touching the metal parts of the refrigerator. To check for breakdown, you need to switch the multimeter to the diode test mode or to the maximum resistance measurement limit (2 MOhm and higher).
Press one probe to any of the three contacts on the compressor, and the second to a clean, unpainted metal part of the motor housing or a copper tube (after cleaning the contact area with a knife until it shines). The device should show infinity (one in the most significant digit). Any other value indicates an insulation breakdown.
⚠️ Attention: If a breakdown is detected on the housing, the operation of such a refrigerator is strictly prohibited! This poses a direct threat to people's lives. Such a compressor can only be recycled or professionally rewinded, which is impractical in domestic conditions.
It is also worth mentioning the interturn short circuit, which is difficult to diagnose with a conventional multimeter. In this case, the resistance of the windings may be normal, but the motor will be