The situation when the refrigerator stops cooling, but there is silence inside or, conversely, a hum is heard without starting the engine, is familiar to many owners of household appliances. In most cases, the cause of the breakdown is the failure of the starting relay or the compressor itself, and the owner is faced with the question: is it worth calling a technician or can you carry out diagnostics yourself.
Checking refrigerator compressor directly is a proven method that allows you to determine with high accuracy whether the motor is alive, or whether the problem lies in the control circuits. If the engine starts from a direct connection, then the relay is faulty and requires replacement, which is an inexpensive repair.
However, before you take up the tools, you must clearly understand the structure of the electrical circuit and follow safety regulations. Working with high voltage requires caution, and incorrect diagnosis can lead to the final failure of an expensive unit or electric shock.
The principle of operation of the starting relay and compressor
To understand the essence of the test, you need to understand how the motor-relay combination works. Compressor is an electric motor immersed in oil with two windings: working and starting. At the moment of switching on, it requires a powerful push to move the pistons and create pressure in the system.
This push is responsible starting relay, which supplies voltage to the starting winding only at the moment of start. As soon as the rotor picks up speed, the relay opens the starting winding circuit, and the engine continues to operate only on the working winding. If this mechanism is broken, the motor hums, but does not start.
Modern models often use PTC relay (posistors), which operate based on changes in resistance when heated, while in older refrigerators electromechanical devices with a coil and a moving contact were installed. This does not change the principle of checking the motor, but the design of the relay is different.
⚠️ Attention: Never leave the compressor turned on directly for more than 5-7 seconds without control. The absence of a standard relay can lead to overheating of the windings and jamming of the piston group.
Understanding these processes is critically important, as it allows you to distinguish a mechanical knock or hum from a real electronic failure. If you hear a characteristic click followed by a buzzing sound, but the shaft does not spin, the likelihood of problems with the trigger mechanism or jamming of the piston is very high.
Necessary tools and safety measures
Before starting any work with electrical appliances, the rule is to completely disconnect the power. Unplug the refrigerator from the socket. To carry out diagnostics, you will need a minimum set of tools, which most home craftsmen can find.
You will need a multimeter (tester) to measure the resistance of the windings, pliers, a screwdriver and, possibly, electrical tape. If you plan to start the motor for testing, you will need a working socket with access to grounding or automatic switch in the panel for quick de-energization.
It would also be a good idea to prepare gloves to protect your hands from the sharp edges of the metal casing of the compressor and possible contamination. Working with 220 Volt electricity always carries risks, so a sober assessment of your strengths is required.
- 🔌 Multimeter or ohmmeter to check the integrity of circuits.
- 🔧 A set of screwdrivers (phillips and flat) for removing the casing.
- 🧤 Dielectric gloves for additional protection.
- 📏 Insulating tape for temporary fixation of wires.
Make sure the work area is well lit and the floor is dry. Wet shoes or standing water on the floor are not permitted during such operations. If you feel unsure of your actions, it is better to stop at the stage of visual inspection.
Dismantling and visual inspection of the starting relay
The process begins by removing the protective casing at the lower rear of the refrigerator. It is usually secured with latches or screws. After removal, you will see a black “barrel” of the compressor and a plastic box attached to its contacts - this is the start relay.
Carefully disconnect the relay. It can be held on by spring brackets or simply removed from the contacts by moving downward. Carefully inspect the device for external damage: melting, cracks, blackening or traces of burning.
If carbon deposits are visible inside the relay or the smell of burnt plastic is felt, this is a sure sign of its failure. In such cases replacing the relay often solves the problem, but it is still necessary to check the compressor itself to make sure the engine is working properly.
When inspecting, pay attention to the contacts on the compressor itself. They must be clean, free of oxides and traces of corrosion. If the contacts are oxidized, they can be carefully cleaned with fine sandpaper before further diagnostics.
Checking the compressor windings with a multimeter
The most reliable method of primary diagnosis is to check the continuity of the windings. The compressor body usually has three contacts arranged in a triangle. After removing the relays, you will see how they correspond to the working, starting winding and common wire.
Switch the multimeter to the resistance measurement mode (Ohm). Measure the resistance between each terminal and the motor housing. The device should show infinity (or one in the most significant digit), which indicates the absence of breakdown to the housing.
Then measure the resistance between the contacts themselves. Between the working and starting windings, the sum of the resistances must be equal to the resistance between the extreme contacts. Typical values for a working engine:
| Measurement parameter | Normal value | Failure sign |
|---|---|---|
| Starting winding resistance | 30-50 Ohm | Open (infinity) or short circuit (0 Ohm) |
| Resistance of the working winding | 10-25 Ohm | Open or short circuit |
| Resistance body-winding | Infinity | Any value (insulation breakdown) |
| Resistance between windings | Sum of the two above | Inconsistency sum |
If the multimeter shows a short circuit (0 Ohm) or an open circuit, further testing by starting does not make sense - the compressor is faulty and requires replacement. In this case, it is more economical to buy a new unit or call a specialist for complex repairs.
Why is the resistance of the windings different?
The starting winding has a thinner wire and a greater number of turns, so its resistance is always higher than that of the working winding, which is thicker wire for operation under load.
Instructions: how to start the compressor directly
If the multimeter showed normal resistance values, you can proceed to checking the startup. To do this, you will need to apply 220V voltage directly to the motor contacts, bypassing the relay. Be extremely careful, as the wires will be live.
First determine which contacts correspond to the working and starting windings. Usually they are located on top of the triangle of contacts, and the common one is at the bottom, but it is better to check the markings on the case or the diagram of a specific refrigerator model. Connect one wire from the plug (phase) to the common contact. Connect the second wire from the plug (zero) to the contact of the working winding. To start, you need to briefly apply voltage to the starting winding. This can be done by touching the wire to the corresponding contact for a split second. refrigerator model.
Connect one wire from the plug (phase) to the common contact. Connect the second wire from the plug (zero) to the contact of the working winding. To start, you need to briefly apply voltage to the starting winding. This can be done by touching the wire to the corresponding contact for a split second.
☑️ Direct start algorithm
If the engine is working properly, you will hear a confident hum and feel vibration. The shaft will start moving. It is important to immediately remove the wire from the starting winding, otherwise it will burn out. The engine must continue to operate on the working winding.
⚠️ Attention: The contact time with the starting winding should not exceed 1-2 seconds. Prolonged application of voltage to the starting winding will lead to its burnout.
During the test, make sure that your fingers and tools do not touch the metal parts of the compressor and exposed wires. It is better to use insulated clamps or “crocodiles.”
Analysis of results and typical errors
After successfully starting the motor, you can directly draw an unambiguous conclusion: the compressor is working, and the problem lies in the start relay or thermostat. In this case, buying a new relay solves the problem in 90% of cases.
If the motor hums, but does not start even with a direct connection, or knocks out the machine in the panel, then there is a mechanical compressor wedge or interturn short circuit. Attempts to “unwedge” the engine are often temporary.
A typical mistake for beginners is confusion in the contacts. If you mix up the working and starting windings with constant connection, the engine will burn out in a matter of minutes. Always double-check the circuit before applying voltage.
Another mistake is ignoring the condition of the wiring. Before checking, make sure that the wires with which you connect the motor have a sufficient cross-section and reliable insulation to withstand the starting current.
Frequent diagnostic questions (FAQ)
Is it possible to leave the refrigerator to operate without a relay?
No, operate the refrigerator without a standard or a working analog relay is not possible. This will lead to rapid overheating and burning of the starting winding or jamming of the compressor.
Why does the compressor hum but does not start?
This may indicate jamming of the piston group, failure of the starting relay (contacts do not close) or a drop in voltage in the network below the permissible level.
How to distinguish a compressor breakdown from a freon leak?
If the compressor is working (humming, hot), but there is no cold, and it does not turn off, it is most likely a freon leak. If the motor is silent or hums and clicks, the problem is in the electrics or mechanics of the motor.
Is it dangerous to check the compressor yourself?
Checking is dangerous only if electrical safety rules are violated. High voltage 220V can be fatal. If you do not have skills in working with electricity, it is better not to take risks.