Sudden Stopping the refrigerator often becomes an unpleasant surprise, disrupting the usual rhythm of life and jeopardizing the safety of food. In most cases, the cause of the breakdown is the failure of the motor-compressor - the “heart” of the cooling system, which ensures the circulation of refrigerant throughout the circuit. Before calling an expensive technician or purchasing new equipment, experienced home craftsmen recommend conducting an initial diagnosis of the electrical part of the engine.
You can determine the performance of the unit at home, using a regular household multimeter. This device will allow you to measure the resistance of the windings, identify a short circuit or open circuit, and also check the insulation for breakdown. Timely diagnostics helps to save significant money, since sometimes the problem lies not in the compressor itself, but in the starting relay or thermostat.
To carry out work You'll need a basic set of tools, including screwdrivers for removing the casing, pliers and, of course, a working multimeter. It is important to understand that any manipulations with electrical equipment require strict adherence to safety precautions. Checking should only be carried out with the device completely disconnected from the network, since a voltage of 220 volts poses a real threat to human life.
Preparatory work and safety measures
The first and most critical stage is the complete de-energization of the refrigeration equipment. Simply turning off the button on the control panel is not enough - you need to unplug the power cord from the outlet. The protective cover located at the lower rear of the unit must then be removed to gain access to the compressor and start relay. It is usually secured with latches or screws that can be easily unscrewed with a Phillips screwdriver.
Carefully inspect the visual condition of the components. There should be no melted insulation on the wires, and no traces of burning or soot on the metal parts. If you notice black marks on the relay contacts or the motor itself, this may indicate serious overheating or a short circuit. In such cases, further operation without replacing burnt parts is impossible and even dangerous.
⚠️ Attention: Before starting any work, make sure that the capacitors in the circuit (if your model has them) are discharged and your hands are dry. Working with electrical appliances requires sobriety and caution.
Prepare a multimeter to take measurements. Switch it to resistance measurement mode (Ohms), selecting the 200 Ohm limit or dial mode. Check the functionality of the tester itself by closing the probes: the device should show zero or emit a beep. If the multimeter shows one or infinity with the probes closed, its battery is low or the device is faulty.
Connection diagram and access to contacts
The refrigerator compressor has three main terminals that come out of its housing and are connected to the start relay. These contacts are arranged in a triangle and are responsible for starting and operating the engine. To ring the windings, you must carefully remove the starting relay and the protective plastic box covering the contact group. This must be done without excessive force so as not to damage the fragile terminals.
On the relay body or in the technical documentation there is usually a diagram indicating the pins. The standard marking is as follows: S (Start) - starting winding, R (Run) - working winding and C (Common) - common wire. Sometimes, instead of letters, numbers or color markings of wires are used, so knowing the diagram of your specific refrigerator model Indesit, Atlant or LG will be useful.
If the marking is erased or missing, contacts can be determined by elimination, knowing the approximate resistance of the windings. The working winding always has less resistance than the starting winding, and between the two extreme contacts the resistance will be total. Correct identification of findings is the key to accurate diagnosis. An error in identification can lead to incorrect conclusions about the condition of the engine.
Diagnostics of windings with a multimeter
The testing process involves measuring the resistance between different pairs of contacts. Touch the multimeter probes to terminals S and C, then R and C, and finally S and R. Record the readings to analyze them. Normal resistance values can vary depending on the power of the motor, but they are usually within certain limits.
The operating winding typically has a resistance in the range of 10 to 30 ohms, while the starting winding has a higher resistance - from 30 to 150 ohms. The total resistance between the starting and operating contacts should be equal to the sum of the resistances of each winding relative to the common wire. If the multimeter readings differ greatly from these values, this is a signal of malfunction.
☑️ Checking the serviceability of the compressor
Let's consider typical reading scenarios in the table below to make it easier for you to interpret the measurement results:
| Indication type | Value on screen | Probable cause | Actions |
|---|---|---|---|
| Normal | 10-150 Ohm | Windings are intact | Check other components |
| Break | 1 or OL (infinity) | Open winding circuit | Replacing the compressor |
| Short circuit | 0 Ohm | Short circuit turns | Replacing the compressor |
| Unstable numbers | Jumping values | Poor contact of probes | Clean contacts |
On hot compressor readings may be higher than when cold. Therefore, if you carry out diagnostics immediately after the refrigerator is running, make an adjustment for the temperature coefficient. For accurate measurements, allow the unit to cool to room temperature.
Checking for housing insulation breakdown
One of the most dangerous faults is an insulation breakdown when voltage hits the metal housing of the compressor. This may result in an electric shock when touching the refrigerator or tripping an RCD in the electrical panel. To check for breakdown, set the multimeter to resistance measurement mode at the maximum limit (usually 200 kOhm or 2 MOhm).
Press one probe to any of the three contacts of the compressor, and press the second firmly to the part of the metal motor housing that has been cleared of paint and rust. With proper insulation, the device should show infinity (one in the most significant digit). Any resistance value, even a few megaohms, indicates a violation of the insulation.
⚠️ Attention: The presence of even a weak leakage current to the housing makes the operation of the refrigerator deadly. Such a unit must be immediately turned off and sent for repair or disposed of.
Sometimes a breakdown appears only under load or when heated. If the multimeter shows normal, but knocks out plugs when turned on, the problem may be in the start relay or capacitor. However, always check the motor first, since replacing it is the most time-consuming part of the repair. Do not ignore the slightest suspicion of current leakage.
Why does it break through the housing?
Insulation breakdown often occurs due to aging of the varnish coating of the windings, moisture getting inside the housing or mechanical damage to the wires during transportation. An internal short circuit may not manifest itself immediately, but gradually destroy the structure of the motor.
Analysis of the starting relay and thermal protection
Often the reason that the refrigerator does not turn on is not the compressor itself, but the starting relay or thermal protection relay. These small devices are responsible for supplying voltage to the starting winding at the time of start and protecting against overheating. If the motor windings are fine, but the motor hums and does not start or clicks, the problem is most likely here.
Remove the relay and inspect it visually. There should be no melting inside, and the contacts should be clean. Ring the thermal relay circuit: when cold it should ring (show zero), and open when heated. The starting relay is checked for compliance with the markings and the absence of mechanical damage to the contacts.
A faulty relay can create the illusion of a compressor failure. If the relay is stuck in the closed state, the starting winding is constantly energized, which causes its rapid overheating and breakdown. Therefore, if you find burnt windings, be sure to replace the starting device, otherwise the new motor will suffer the same fate.
Typical errors in diagnostics
Beginners often make mistakes that lead to incorrect diagnosis. One common problem is poor contact of the multimeter probes with the terminals. An oxidized layer of metal can give false resistance, which can be mistaken for an open circuit. Always clean the contacts to a metallic shine before taking measurements.
Another mistake is ignoring the condition of the wires going to the compressor. A frayed or broken wire in the harness can break the circuit, and the multimeter will show a broken winding, although the motor itself is working. Carefully feel all the way from the plug to the motor contacts. Also, do not forget about the possibility of a malfunction of the measuring device itself.
Do not try to “revive” the compressor by applying voltage directly, bypassing the relay, unless you are a qualified electrician. This can lead to a capacitor explosion or complete burnout of the windings. Safety and methodicality are the main principles of successful repair.
When a compressor replacement is necessary
Replacement compressor is a complex and expensive process that requires special equipment to evacuate the system and charge the refrigerant. If the diagnostics showed a break or short circuit in the windings, or a breakdown in the housing, replacement is inevitable. It is almost impossible to perform this operation on your own without skills and tools.
The cost of a new motor-compressor and its installation often constitutes a significant part of the price of a new refrigerator. Therefore, if your unit is more than 10-12 years old, sometimes it makes more economic sense to purchase new equipment than to repair the old one. However, for modern models, replacing the compressor is the only way to extend the life of the device.
When purchasing a new compressor, pay attention to its power, type of refrigerant and overall dimensions. Installing a more powerful or less powerful motor will upset the balance of the refrigeration system. Entrust the final installation and refilling of freon to certified specialists to guarantee long service life of the equipment.
Is it possible to restore a burnt-out compressor?
Restoring a burnt-out compressor at home is impossible. Burnt-out windings require rewinding under special conditions using high-temperature varnish and vacuum drying, which is not economically feasible. It’s easier and more reliable to buy a new unit.
Why does the compressor hum, but does not start?
A hum when it does not start most often indicates a jammed piston group or a faulty start relay. If the relay is working properly, and the motor hums and heats up quickly, the mechanical part of the engine is probably jammed.
What resistance should be between the contacts?
The exact values depend on the model, but usually: between general and working - 10-30 Ohms, between general and starting - 30-150 Ohms, between working and starting - the sum of the two previous values. The main thing is the absence of infinity (break) and zero (short circuit).
Is it dangerous to repair a refrigerator yourself?
Electrical diagnostics are safe when the power is turned off. However, work related to the freon circulation system (depressurization, soldering, refilling) requires a license and special equipment, since the refrigerant can be dangerous, and the system requires evacuation.