The lack of cold in the refrigerator compartments is often accompanied by silence: the motor does not hum and does not start. This is a sure sign that electrical circuit it is broken or the engine has failed. Before calling a specialist, many owners try to understand the essence of the problem on their own. The first and most accessible diagnostic method at home is testing the windings of the compressor using a multimeter.
This procedure allows you to determine the integrity of the windings and the absence of breakdown on the housing. If you know how to handle tools and follow safety precautions, you can quickly find out whether unit it can be restored or requires replacement. In this article we will analyze in detail the process of preparing, taking readings and interpreting measurement results.
⚠️ Attention: Before starting any diagnostic work, be sure to disconnect the refrigerator from the electrical network. Working with current requires extreme caution, as capacitors can retain a residual charge.
Necessary tools and preparation
To carry out high-quality diagnostics, you will need a basic set of tools. The main device is multimeter (tester). It can be either pointer or digital, the main thing is that it works properly in resistance measurement mode. You will also need screwdrivers for dismantling the protective casing and insulating tape for subsequent assembly.
Preparation of the workplace plays an important role. Ensure good lighting in the compressor area as the contacts may be hidden in the shadows. If the refrigerator is built-in, it must be pulled out to provide free access to the rear wall. The engine should be cool if it tried to start before.
☑️ Preparation for diagnostics
It is important to visually check the condition of the wires and connectors. Sometimes the reason for the lack of starting lies not in the motor itself, but in oxidized contacts or a broken wire. Start relay also must be removed to access the compressor terminals. Make sure that there are no traces of burning or melting on the contacts.
Connection diagram and pin layout
The refrigerator compressor usually has three terminals forming a triangle. They are responsible for connecting the starting and working windings, as well as the common point. On modern models, the terminals may be marked with letters or symbols, but often the markings are erased or missing. In this case, you need to know the standard layout.
If you look at the contacts from above (with the relay removed), they form a triangle. The top contact is general terminal (Common). The lower left is the starting winding (Start), the lower right is the working winding (Run). However, the location may vary depending on the manufacturer, so you cannot rely on geometry alone.
Marking of terminals on different brands
On Danfoss (Secop) compressors, terminals are often marked as C (common), S (start), R (run). On domestic models, there may be no markings, then they rely on the resistance of the windings.
To accurately determine the terminals, the resistance measurement method is used. The working winding always has less resistance than the starting winding. The sum of the resistances of both windings is equal to the resistance between the starting and working terminals. This is a key principle that will help you not get confused in contacts.
Safety precautions when working with electricity
A refrigerator is a complex electrical device operating on a 220 Volt network. Failure to follow safety instructions may result in electric shock or equipment failure. Even after unplugging from the outlet, dangerous potentials may remain in the circuit.
Never touch exposed live wires. Carry out all manipulations with the multimeter only on a de-energized device. If you find melted wiring or a burning smell, it is better to entrust further diagnostics to professionals, since not only enginecould be damaged, but also the wiring of the refrigerator itself.
Pay special attention to grounding. If your refrigerator is not grounded, static electricity or insulation potential may accumulate on its body. Work in dry shoes and in a room with normal humidity levels. A wet floor is a direct path to electrical injury.
The process of testing the windings with a multimeter
After removing the start relay, you will be left with three contacts of the compressor. Set the multimeter to resistance measurement mode (ohms). Select the minimum measurement limit (usually 200 Ohms). First find the general conclusion. To do this, alternately measure the resistance between pairs of contacts.
The pair of contacts that gives the highest resistance is the starting and operating windings together. The third, remaining contact is general output. Now, knowing the common terminal, measure the resistance between it and each of the other two. A lower value will indicate the working winding, a larger value will indicate the starting winding.
Write down the values obtained. They must be stable and not change randomly. If the device shows one (infinity) or zero, this indicates a malfunction. Normal resistance values for a working motor usually range from 10 to 50 Ohms for the working winding and from 30 to 100 Ohms for the starting winding, depending on the power and model.
Analysis of results and table of faults
The data obtained must be correctly interpreted. Deviations from the norm may indicate different types of breakdowns. Below is a table that will help you navigate the instrument readings and determine the condition of the electric motor.
| Multimeter readings | Between which terminals | Probable cause | Solution |
|---|---|---|---|
| Infinity (1) | Any pair | Winding break | Replacement of the compressor |
| Zero (0) | Any pair | Short circuit | Replacement of the compressor |
| Normal (10-100 Ohm) | All pairs | Windings are intact | Checking the relay and thermostat |
| Falls to zero | When heated | Interturn short circuit | Replacement compressor |
If the multimeter shows infinity, it means the circuit is open. It could be an internal wire break in the coil. In the event of a short circuit (zero ohm), a twisting of the turns or a breakdown of the insulation inside the housing occurs. Both cases require replacement of the unit, since rewinding at home is impossible and economically unfeasible.
It is important to note that the resistance of the windings may vary slightly depending on the temperature of the motor. Cold engine has less resistance than a hot one. However, these fluctuations should not be critical. If the values fit within the norms, but the refrigerator does not work, the problem may be in the starting relay or thermostat.
Checking for insulation breakdown (short to the case)
The most dangerous malfunction is the breakdown of winding insulation on the metal body of the compressor. In this case, tension may appear on the housing, which is fatal to humans. You can also check this using a multimeter, but you need to be sure that the device is working properly.
Press one multimeter probe to any of the three contacts of the compressor block (first clean the contact area from oxides, if necessary), and press the second probe to the unpainted part of the metal engine housing. It is best to scrape off some paint or find a grounding bolt.
⚠️ Attention: If the device shows at least some resistance (the needle has moved or the numbers have changed), then the insulation is broken. It is STRICTLY PROHIBITED to operate such a refrigerator.
In good condition, the resistance between the windings and the body should be infinite. The multimeter should show one in the most significant digit. Even a small resistance indicates that current may be flowing to the housing. This often happens after prolonged use or moisture getting inside the casing.
Additional reasons for startup failure
If the continuity test shows that the windings are intact and there is no breakdown in the housing, but the engine still does not start, the reason may lie in the attachments. Often it fails starting relay, which supplies an impulse to the starting winding. It can also be checked for the integrity of the contacts and the absence of carbon deposits.
Another culprit is the thermostat. If it does not close the circuit when the temperature in the chamber rises, the start signal simply does not arrive. Test it by shorting the contacts directly (temporarily). If the engine hums, change the thermostat. It is also worth checking the integrity of the supply cable and plug.
The role of the capacitor in starting
Some models of refrigerators use a starting capacitor. If it is swollen or has lost capacity, the engine will hum but will not start. It also needs to be checked with a tester.
Do not forget about mechanical reasons. If the compressor is mechanically jammed (cylinder wear, scuffing), electrically it may be fine, but it will not be able to start. In this case, when you try to start, it will hum strongly and quickly heat up, after which the thermal protection will work.
Frequently asked questions (FAQ)
Is it possible to check the compressor without a multimeter?
It is impossible to qualitatively check the windings without a device. You can only visually inspect for burning or try to run directly through the cord with a plug (the method is dangerous and requires skills), but this will not provide information about the state of insulation and the exact resistance.
What resistance is considered normal for different brands?
Norms may differ. For Indesit and Atlant the working winding is usually 10-20 Ohms, the starting winding is 30-40 Ohms. For powerful industrial compressors, the resistance may be less (2-5 Ohms). The main thing is the ratio: the starting resistance always has greater resistance than the working one.
What to do if the resistances of the windings are the same?
In some circuits (rarely) or in the event of certain faults, the resistances may be close. However, in a classic single-phase refrigerator motor they should be different. If the difference is minimal, an interturn short circuit is possible, which is difficult to detect with a multimeter - you need a megohmmeter.
Is it possible to repair a burnt winding?
Theoretically, it is possible to rewind, but in practice this requires special equipment, removing the casing, welding and vacuuming the system. The cost of such work will exceed the price of a new compressor. Therefore, if there is a break or short circuit, the entire engine is replaced.