A sudden stop of the refrigeration chamber is always an unpleasant surprise that can spoil food supplies and disrupt the usual way of life. Most often, the cause of a breakdown is a failure compressor, which is the heart of the entire cooling system. Before calling a technician or buying a new unit, it makes sense to conduct an initial diagnosis to understand whether the motor can be restored.
In this article we will look in detail at how to ring a refrigerator motor using available tools. You will learn about methods for checking the integrity of windings, ways to detect a breakdown on the frame and the nuances of measuring resistance. Understanding these processes will allow you to save money on calling a specialist for a simple diagnosis or make sure that serious repairs are necessary.
It is worth noting that electric motors in modern and older models, be it Indesit, Atlant or Bosch, have a similar design. However, the diagnostic approach may vary depending on the type of compressor (linear or inverter). We will focus on classic linear models, which make up the majority of household appliances.
Required tools and safety measures
Before starting any work with electrical equipment, you must ensure your safety and prepare your working tools. The main diagnostic device will be multimeter (tester), which allows you to measure resistance, voltage and check the integrity of the circuit. Without this device, accurate diagnostics is impossible, since visual inspection often does not reveal internal defects in the windings.
⚠️ Attention: All work on checking the electrical circuits of the refrigerator should be carried out exclusively with the power supply disconnected from the network. Residual voltage in the capacitors can lead to electric shock, so let the equipment stand turned off for 15-20 minutes before starting work.
In addition to a multimeter, you will need a set of screwdrivers to dismantle the back panel and remove the compressor casing. It would also be a good idea to have electrical tape, a marker for marking wires, and possibly pliers on hand. If you plan to carry out more in-depth diagnostics, you may need a megohmmeter, but for a basic check at home, a high-quality digital tester is sufficient.
It is important to prepare a work area with good lighting. You will have to work in a confined space at the back of the refrigerator, where dust and cobwebs often accumulate. Carefully clean the area around the motor with a dry cloth to prevent dirt from getting inside the electrical contacts when opening them. This will prevent false readings of the device due to contamination.
☑️ Preparation for diagnostics
Access to the electrical part of the compressor
To ring the motor windings, you need to gain physical access to its contact group. To do this, carefully move the refrigerator away from the wall and remove the back metal cover that covers the compressor compartment. In some models, for example, in refrigerators LG or Samsung, access may be partially limited by structural elements that require careful handling.
On the compressor itself there is a plastic or metal casing that covers the starting and protective relay. It is usually secured with snaps or a single screw. When you remove the cover, you will see three contact pins coming out of the motor housing, to which the relay terminals are connected. It is these contacts that we will need to check.
Before touching the contacts, carefully inspect their condition. The presence of carbon deposits, oxides or melted insulation may indicate overheating or poor contact, which often accompanies winding problems. If there are no visual defects, you can proceed to instrumental testing. Carefully remove the starting relay to free the contacts for the multimeter probes.
Checking the integrity of the motor windings
The main task at this stage is to determine whether there is a break in the stator windings of the electric motor. A refrigerator compressor usually has two main operating windings: starting and operating windings, as well as a common point. The resistance of the starting winding is usually higher than that of the working winding due to the use of a wire with a smaller cross-section.
To check, switch the multimeter to the resistance measurement mode (Ohm). Touch the probes to the pairs of contacts. You need to get three values: between general and working, between general and triggering, and between working and triggering. The sum of the two smaller resistances should be equal to the largest (resistance between the extreme contacts). If the device shows one or infinity, there is open circuit, and the engine is faulty.
Normal resistance values depend on the power and model of the compressor, but usually range from 10 to 35 Ohms for the starting winding and from 2 to 15 Ohms for the working winding. A significant downward deviation from these values may indicate an interturn short circuit, which we will discuss below. Accurate data can often be found in the technical documentation for a specific model, for example, for compressors Danfoss or Secop.
The table below shows approximate resistance values for different types of windings that you should focus on:
| Winding type | Approximate resistance (Ohm) | Characteristic signs of serviceability |
|---|---|---|
| Working | 2 - 15 Ohm | Lowest resistance |
| Starting | 15 - 40 Ohm | Resistance is higher than the working one |
| Between contacts | Sum Rstart + Rwork | Equal to the sum of the other two |
| On body | Infinity (∞) | There should be no breakdown |
Diagnostics of breakdown on the housing (Short circuit)
One of the most dangerous malfunctions is breakdown of the winding insulation on the metal body of the compressor. In this case, the engine can work, but the housing will be under voltage, which creates a direct threat to human life if touched. In addition, such a malfunction often leads to knockout of circuit breakers in the electrical panel.
To check for a breakdown, switch the multimeter to the continuity mode or resistance measurement to the maximum limit. Press one probe tightly to a stripped metal area of the compressor body (for example, to the soldering point of a copper tube or a specially stripped area), and with the second one touch all three motor contacts in turn.
If the device shows any resistance value other than infinity, or emits a sound signal in the dialing mode, it means that the insulation is broken. Operate such a refrigerator strictly prohibited. Even if it works temporarily after replacing the relay, the risk of electric shock remains critical. In such cases, replacement of the compressor or professional rewinding is required, which is often impractical in domestic conditions.
Why does breakdown occur on the housing?
Insulation breakdown most often occurs due to overheating of the motor, when the varnish covering the windings dries and cracks. Also, the cause may be moisture getting inside the motor during poor transportation or storage, or mechanical damage to the windings due to vibration.
Identification of interturn short circuit
The most difficult problem to diagnose at home is the problem of interturn short circuit. In this case, the turns of the winding close together, which leads to a sharp decrease in resistance and, as a consequence, to a multiple increase in current strength. In this case, the engine can hum, get very hot and quickly turn off by the thermal relay, but formally “ring” as a whole circuit.
An indirect sign of an interturn short circuit is an abnormally low resistance of the windings compared to the passport data. If you see values 2-3 times lower than normal, this is an alarming signal. A short circuit can also be indicated by the fact that the compressor starts, runs for a few seconds, and then the protection is triggered and the cycle repeats.
For more accurate diagnostics, professionals use current clamps. When starting a working compressor, the current consumption corresponds to the rating indicated on the tag. If the current significantly exceeds the rated values (for example, instead of 1 A, 5-6 A flows) immediately after startup, this is an almost guaranteed interturn short circuit. Visually, the windings in this case often have blackening or a burning smell, but this can only be seen after disassembling the stator.
Checking the starting and thermal relay
Often the reason that the refrigerator does not turn on is not the engine itself, but a malfunction of the starting relay or thermal protector. These elements are attached to the contact group of the compressor and are responsible for starting the motor and protecting against overloads. Before damaging the windings, it is necessary to prevent their damage.
The thermal relay is checked for an open circuit. When cold, it should “ring” (resistance is close to zero). If the circuit is open, the relay is burnt out and requires replacement. The starting relay is checked visually for cracks and burning, and also rings. Inside, it may contain a coil or a posistor, which fail over time.
Replacing these components is simple and inexpensive. The main thing is to choose a relay with exactly the same characteristics as the old one, since they are designed for a specific compressor power. Installing the wrong relay may result in the motor not starting or the winding burning out due to the starting circuit being energized for a long time.
⚠️ Attention: If, after replacing the relay and checking the windings, the compressor still does not start or the machine breaks down, the problem may lie in the wiring of the refrigerator itself or the control module. Do not try to start the motor bypassing the protective devices - this is guaranteed to lead to its combustion.
FAQ: Frequently asked questions
Is it possible to check the compressor without a multimeter?
Completely check the condition of the windings without measuring instruments is impossible. However, you can perform a visual inspection for burning and try to apply voltage directly (only for experienced ones!), but this is risky. The absence of a buzz when connected to the network may indicate a break, but only a tester will make an accurate diagnosis.
What resistance is considered normal for a household refrigerator?
The norm depends on the power of the motor. For standard refrigerators with a volume of 250-350 liters, the resistance of the working winding is usually 10-20 Ohms, and the starting winding is 20-40 Ohms. It is critically important that there is no breakdown to the housing (the resistance must be infinite).
Why does the compressor hum but does not start?
This may be caused by jamming of the piston group (mechanical failure), a malfunction of the starting relay, which does not supply a pulse to the starting winding, or an interturn short circuit, due to which the motor does not have enough power to start.
Is it worth repairing a compressor with an interturn short circuit?
At home, it is impossible to rewind a hermetic type compressor. Special equipment is required for opening, rewinding, vacuuming and sealing. It is more economically feasible to replace the compressor with a new one or a used one in good condition than to try to restore the old one.