Sudden stop of the refrigerator or its inability to maintain the set temperature often causes panic, because this threatens food spoilage. However, before calling a technician or buying new equipment, it is worth conducting an initial diagnosis to understand where the problem lies. In most cases, the breakdown is associated with the compressor "heart" of the refrigeration unit, which ensures the circulation of the refrigerant.
You can determine whether the motor-compressor is working by the characteristic hum, vibration of the housing and the temperature of the condenser grille at the rear. However, external signs do not always provide a 100% guarantee of the serviceability of internal components. Sometimes the unit hums, but does not pump freon, or is completely silent, although electricity is supplied to it. In this material, we will examine in detail how to independently check starting relaythe motor windings and thermostat in order to accurately identify the cause of the malfunction.
To carry out high-quality diagnostics, you will need a minimum set of tools: a screwdriver, pliers and, preferably, multimeter (tester). Without a measuring device, the accuracy of checking the electrical circuit will be low, so it is highly recommended to have one on hand. Remember that any work related to electrical components must be carried out with the device completely disconnected from the network to avoid electric shock.
Primary visual and acoustic diagnostics
The first step is always an external inspection and listening to the working (or trying to start) unit. Go to the refrigerator and listen: if you hear a smooth, quiet hum that turns into gurgling, then the compressor is working properly. If there is silence or clicks are heard, but there is no startup, the problem is obvious. Pay attention to vibration —a working motor creates a barely noticeable vibration, which can be felt by placing your hand on the side wall.
Inspect the back wall of the refrigerator, where the radiator grille is located. If the compressor is functioning properly, this grate should heat evenly. A cold radiator while the engine is running indicates a freon leak or a blockage in the system, and not a breakdown of the engine itself. It is also worth checking the integrity of the wires going to the compressor: they should not be melted or cut through.
⚠️ Attention: If, when you try to start, you hear a loud click, followed by a hum, and after a few seconds another click and silence, immediately turn off the device. This is a sign that the motor is trying to start, but starting relay or the windings are faulty, and prolonged attempts can completely damage the unit.
Often the reason for the silence of the refrigerator is a banal lack of voltage in the outlet or damage to the power cord. Check if the light inside the chamber lights up when the door is opened. If there is no light, check the outlet using another electrical appliance. Make sure that thermostat is not turned to the "minimum" or "off" position, since in this mode the compressor will not receive a command to start.
Checking the start relay and thermostat
If the power supply is okay, The next step is to check the control circuit. Most often, what fails starting relay is a small block attached to the side of the compressor. It is this that gives the impulse to start the engine. To check it, you need to remove the back cover (crankcase) of the refrigerator, unscrew the fasteners and carefully remove the plastic casing from the compressor itself.
Remove the relay from the contacts of the compressor and shake it near your ear. If a rattling sound is heard inside, similar to the clinking of coins, it means that the core is broken or the contacts are burnt, and the part requires replacement. Visually inspect the contacts: the presence of carbon deposits, melted plastic or a characteristic burning smell indicates a short circuit. For a more accurate check, you can use a multimeter in continuity mode.
- 🔌 Disconnect the wires from the relay and check the continuity of the circuit between the contacts.
- 🔍 Inspect the contacts for oxidation and blackening.
- 👂 Shake the relay - the absence of sound indicates integrity core.
- 📏 Ring the compressor windings through the relay contacts to prevent short circuits.
It is also worth checking thermostat. If it is faulty, it may not complete the circuit, and the signal to start the compressor simply does not arrive. To check, you need to close the thermostat contacts directly (after disconnecting the refrigerator from the network!). If after this procedure and connecting to the network the compressor started working, then the problem was precisely in the temperature sensor.
How to properly remove the start relay?
First disconnect the refrigerator from the network. Remove the rear protective panel. Locate the box on the side of the compressor. Carefully bend the retaining brackets or remove the screws. Remove the relay by pulling it down, after noting or photographing the position of the wires. Do not use excessive force to avoid breaking the plastic fasteners.
Diagnostics of compressor windings with a multimeter
The most accurate way to determine the condition of the electric motor is testing the windings with a multimeter. The compressor has three terminals: two working (starting and working windings) and one common. On modern models they are often marked, but it is better to focus on the diagram or measure the resistance between pairs of contacts.
Switch the multimeter to resistance measurement mode (Ohms). First, find the common point: measure the resistance between each pair of contacts. The pair that gives the greatest resistance is the two windings, and the third, remaining contact is general. Next, we measure the resistance between the common contact and each of the other two. The resistance of the starting winding is always higher than the working winding.
| Winding type | Normal resistance (Ohm) | Failure sign |
|---|---|---|
| Working winding | 10 - 25 Ohm | Infinity (open) or 0 (short circuit) |
| Start winding | 20 - 40 Ohm | Infinity (break) or 0 (short circuit) |
| Case (mass) | Infinity (∞) | Any value (breakdown to case) |
| Thermal relay | 0 Ohm (closed) | Infinity (open circuit) |
If the multimeter shows "infinity" (one on the left on the display) between any winding terminals, it means in the circuit break. If the device shows zero or a value close to zero where there should be resistance, a short circuit of the turns has occurred. In both cases, repairing the compressor is impractical - it needs to be replaced.
Analysis of current consumption and pressure
Current clamps are often used for professional diagnostics. This method allows you to evaluate the operation of the compressor under load without disassembling the electrical circuit. Normal current consumption for household refrigerators with a power of 100-200 W is from 0.3 to 0.6 Amperes in operating mode. At the moment of startup, the current may briefly jump to 1-1.5 Amperes.
If, when turned on, the current sharply increases to maximum values and thermal protection is triggered, this indicates interturn short circuit in the windings or jamming of the piston group. If the current consumption is significantly lower than normal (for example, 0.1 A), and the compressor is running, this may indicate a lack of load due to a refrigerant leak or leaking valves.
A more complex method is to check the pressure at the compressor outlet using a pressure gauge station. A pressure gauge is connected to the process pipe (usually it is sealed, but some models have a fitting). If the compressor is working properly, the pressure should increase quickly. If the arrow stands still or grows extremely slowly, it means that the compressor is not pumping.
- 📉 Low current + running motor = possible freon leak.
- 📈 High current + shutdown = interturn short circuit or wedge.
- ⚖️ Pressure does not increase = wear of the valve group or pistons.
- 🌡️ Heating of the housing = overheating due to prolonged operation or poor ventilation.
⚠️ Attention: Checking the pressure requires bleeding off the remaining refrigerant if the system was broken. Freon can be dangerous if inhaled in high concentrations and requires disposal according to environmental standards. Do not carry out this procedure in a closed, unventilated room.
Causes of compressor failure
Understanding the causes of failure helps to avoid a recurrence of the situation in the future. The most common reason is overheating. It occurs due to poor ventilation (the refrigerator is located close to the wall), contamination of the condenser grille with dust, or prolonged operation in a hot room. Thermal protection may not have time to operate, and the insulation of the windings will begin to deteriorate.
The second enemy is power surges in the network. Sudden changes can damage the start relay or pierce the insulation of the windings. The use of high-quality voltage stabilizer significantly extends the life of the compressor. Frequent switching on and off also has a negative impact, for example, if the user constantly opens the door or loads warm food.
Natural wear of mechanical parts - pistons, valves and bearings - is inevitable. The service life of modern compressors is 10-15 years. However, if transported incorrectly (if the refrigerator was transported lying down without observing the settling time), oil could get into the circuit, which leads to water hammer and rapid failure of the unit.
Can it be repaired or does it need replacement?
The issue of compressor repair often confuses owners. Theoretically, it is possible to rewind the windings or replace the valves, but in practice this requires factory conditions, special equipment and high qualifications. The cost of such work at a service center often exceeds the price of a new compressor. Therefore replacing the unit is the only rational solution.
If diagnostics showed a faulty start relay or thermostat, you can replace these parts yourself or at minimal cost. They are inexpensive and sold in parts stores. The main thing is to choose an analogue with exactly the same characteristics indicated on the body of the old part.
When replacing the compressor itself, you must also replace filter drier and evacuate the system before filling with freon. Without a vacuum sealer, moisture and air will remain in the system, which will lead to the formation of ice plugs and corrosion from the inside. Therefore, it is better to entrust a full-fledged repair with replacement of the motor to licensed professionals.
How much does it cost to replace a compressor in 2026?
The cost consists of the price of the unit itself (from 4,000 to 12,000 rubles depending on model and brand) and the cost of the craftsman’s work (from 3,000 to 6,000 rubles). Departure, freon refilling and consumables are also paid for. The total amount is often 50-70% of the price of a new refrigerator, which makes repairs economically justified only for premium appliances or relatively new models.
Why does a new compressor get hotter than the old one?
Modern compressors, especially inverter types, operate at higher housing temperatures to increase energy efficiency. The cause may also be incorrect refrigerant charging (too little or too much) or insufficient operating time to reach the operating mode. If the temperature exceeds 80-90 degrees and a burning smell is felt, operation should be stopped.
Is the faulty compressor humming?
Yes, the nature of the sound may change. A faulty bearing makes a whining or grinding noise. The knock of the piston group sounds like a metallic clang. If the compressor hums but does not start (intermittent humming), this often indicates a mechanical wedge or a problem with the starting winding. A quiet, uniform hum is a sign of normal operation.
How to extend the life of the compressor?
Regularly clean the rear grille of dust, do not place the refrigerator close to the wall (a gap of at least 10 cm is required), do not load hot foods and make sure the door seal is in good condition. It is also important to ensure stable voltage in the network. These simple measures can increase the service life of the unit by several years.
☑️ Diagnostics before calling a technician
In conclusion, it is worth noting that timely diagnostics can save significant money. If you find that compressor does not work, do not rush to throw away the refrigerator. In half of the cases, the problem is solved by replacing a cheap relay or thermostat. However, if the continuity test shows a break or short circuit in the windings, get ready for serious repairs or purchase of new equipment.