The situation when the refrigerator stops cooling, and the temperature inside increases, close to room temperature, always takes you by surprise. Most often, the culprit of such a malfunction is compressor the heart of any refrigeration unit, which is responsible for the circulation of the refrigerant. However, before calling a technician or buying a new unit, it is worth conducting initial diagnostics to make sure that the problem lies in the engine, and not in a freon leak or a malfunction of the thermostat.
Independent testing requires caution, since you will be dealing with high voltage electric current and a complex mechanical assembly. In this article we will analyze a step-by-step algorithm of actions that will help determine the condition motor compressor, measure the resistance of the windings and identify possible short circuits. Understanding the principles of operation of this unit will allow you to avoid unnecessary expenses and accurately formulate the problem when calling for service.
Primary visual and acoustic diagnostics
The first stage of any diagnosis is an external examination and analysis of the sounds produced by the equipment. Often, characteristic signs of a malfunction can be noticed without disassembling the back panel of the refrigerator. Plug in the unit and listen: a working compressor emits a smooth, quiet hum, which periodically subsides when the set temperature is reached. If you hear a loud metallic knock, clicks, or a hum that ends abruptly a few seconds after starting, this is an alarming signal.
Pay attention to the temperature of the compressor housing itself. During normal operation, it heats up, but should not become so hot that it cannot be touched. Excessive heating often indicates an interturn short circuit or problems with the motor cooling system. Also inspect the tubes and the body itself for oily stains - oil may leak through the seals when the system is depressurized.
⚠️ Attention: If, when turned on, the refrigerator makes a loud crack and immediately knocks out the machine in the panel, immediately disconnect the device from the network. Repeated attempts to turn on may lead to a fire in the wiring or complete failure of the apartment's electrical circuit.
To more accurately determine the source of noise, you can use a simple technique: carefully place your hand on the compressor housing (observing safety precautions) and feel the vibration. Rotary engine should vibrate evenly. If the vibration is chaotic or accompanied by strong kickback into the tubes, the internal valves or bearings may be damaged. In some cases, the motor may hum, but not start, which often indicates a jammed piston group or a malfunction of the starting device.
Checking the starting relay and electrical circuit
Before sinning on your own motor, it is necessary to exclude a malfunction of the starting relay. This small element is responsible for supplying a starting pulse to the motor winding. If the relay is stuck or burned out, the compressor will not be able to start, although electricity will flow to it. Remove the protective cover from the back of the refrigerator to gain access to the black compressor barrel, where the relay is attached.
Carefully remove the start relay, disconnecting it from the compressor contacts and wires. Visually inspect the housing for melting, cracks or burn marks. Inside the device there is a coil and a movable core; if the core is jammed or the contacts are oxidized, the relay must be replaced. You can check its performance by shaking it next to your ear - a working element should not make rattling sounds from dangling parts.
- 🔌 Contacts: Sand the contact pads on the relay and the compressor mating part with fine sandpaper if oxide is visible on them.
- 🧲 Magnetic starter: Make sure that the moving part moves freely inside the relay body under the influence of gravity.
- 🔋 Wire integrity: Check the wires going to the relay for breaks or melted insulation.
Often the cause of failure is not the compressor itself, but the control circuit. If after replacing the relay (which is inexpensive) the situation has not changed, the problem lies deeper.
Testing the windings with a multimeter
The most A reliable way to check the electrical part of the engine is to measure the resistance of the windings using a multimeter. For this procedure, you will need to remove the relay and gain access to the three contacts on the compressor housing. They are usually arranged in a triangle. Switch the multimeter to the resistance measurement mode (Ohm) to the limit of 200 Ohm or 2 kOhm.
Find the paired contacts corresponding to the starting and working windings, as well as the common terminal. The resistance between them should be from 10 to 30 Ohms for the working winding and slightly higher for the starting winding. The exact values depend on the motor power and model of the refrigerator, for example, for Danfoss or Secop parameters may differ from domestic analogues. If the device shows one (infinity), it means there is a break in the winding and the motor is faulty.
Pay special attention to checking for breakdown on the housing. Press one multimeter probe to any of the contacts, and the second to the place on the metal body of the compressor that has been cleared of paint. The device should show infinity. If you see any resistance values, this means insulation breakdownthat makes the operation of such a refrigerator deadly.
| Measurement type | Normal reading | Failure sign |
|---|---|---|
| Working winding | 10 - 30 Ohm | Open (∞) or short circuit (0 Ohm) |
| Starting winding | 20 - 40 Ohm | Open (∞) or short circuit (0 Ohm) |
| Breakdown to body | Infinity (∞) | Any resistance value |
| Thermal protection | 0 Ohm (closed) | Open circuit when the motor is cold |
It is important to take measurements on a completely cooled compressor, since the internal thermal protection may be open when hot, which will give a false signal about an open circuit. If after cooling for 30-40 minutes the circuit is not restored, the thermal relay inside the motor also requires replacement or diagnostics.
Why may the resistance of the windings differ?
The resistance depends on the thickness of the wire and the number of turns. The starting winding usually has a higher resistance, as it is designed for short-term operation. The difference in readings between different models of compressors can reach 20-30%, so always check the technical documentation of the specific brand.
Diagnostics of the mechanical part and pressure
If the electrical part is in order, the problem may lie in the mechanics. A compressor is a complex pump, and if its piston group is worn out or coked, it will not be able to create the necessary pressure to circulate freon. You can check this by connecting to the service fitting (if there is one) or soldering in a temporary pressure gauge manifold. Normal suction pressure should be about 0.1 MPa, and discharge pressure should be much higher.
There is a “folk” method for checking performance, which is often used by craftsmen. A piece of tube is placed on the compressor outlet (discharge) and the motor is turned on. A working unit should blow air forcefully, creating a noticeable stream. If the air barely quivers the flame of a candle or a sheet of paper pressed to the tube, it means that the compressor “does not pump.”
⚠️ Attention: When checking pressure and working with tubes, do not pinch copper pipelines with pliers. Thin walls can collapse, blocking the flow of refrigerant, which will require complex repairs with replacement of a section of the line.
Another sign of a mechanical malfunction is a jammed rotor. If, when voltage is applied, the motor hums and jerks, but the shaft does not turn, the bearings or piston group may be jammed. In some cases, a short-term supply of increased voltage through a special unit helps, but at home it is better not to use this method due to the risk of completely killing the engine.
Analysis of current consumption
One of the most accurate diagnostic methods without opening the system is to measure current consumption. For this you will need current clamps. The normal operating current of a compressor is usually between 0.3 and 0.8 Amps depending on the power and model. A significant excess of these values indicates an overload of the motor.
If the current at the moment of starting jumps sharply to 3-5 Amperes and immediately knocks out the protection, this is a sure sign of a short circuit in the windings or mechanical jamming. If the current is below normal, but the compressor is working, this may indicate dry operation due to a lack of freon or loss of compression. Measurements must be carried out with the engine running, covering one of the power wires with clamps.
- 📉 Low current: Indicates operation without load (freon leakage, loss of compression).
- 📈 High current: Indicates an interturn short circuit, jamming or problems with capacitor (in two-phase motors).
- ⚡ Current surges: Chaotic changes in readings may indicate unstable voltage in the network or a relay malfunction.
Compare the data obtained with the passport values for your models. For example, compressors LG or Samsung inverter type have a different current consumption profile than classic linear models. Inverters smoothly change the rotation speed, so their current will vary over a wide range depending on the load.
☑️ Compressor diagnostics
Frequent causes of failure
Understanding the causes of failure helps prevent the situation from reoccurring in the future. Most often, compressors die not due to manufacturing defects, but due to improper operation. The main enemy is overheating. If the refrigerator is close to the wall, the radiator on the back wall is not blown, and the motor works with increased load, trying to compensate for poor heat transfer.
The second common reason is power surges. Even if the refrigerator has protection, constant fluctuations can gradually destroy the insulation of the windings or damage the starting electronics. The use of a surge protector or voltage stabilizer significantly extends the life of the compressor.
The third reason is a violation of the tightness of the system. The entry of moisture or air into the circuit leads to the formation of acids that corrode the motor windings from the inside. This often happens during poor-quality previous repairs, when the system was not properly evacuated.
FAQ: Frequently asked questions
Is it possible to repair a burnt-out compressor yourself?
Replacing burnt windings at home is impossible. To do this, you need special equipment for rewinding and sealing the case in a vacuum. The only repair option is to completely replace the compressor with a new one, which requires skills in soldering copper tubes and refilling with freon.
Why is the compressor hot, but the refrigerator does not freeze?
This may indicate a loss of compression (wear of the piston group) or a refrigerant leak. The motor runs and heats up, but does not create the necessary pressure to circulate gas through the system. Diagnostics of the pressure in the circuit is required.
How much does it cost to replace a compressor?
The cost consists of the price of a new unit (from 3,000 to 10,000 rubles depending on the model) and the cost of the technician’s work (filling with freon, soldering, replacing the filter-drier). On average, repairs cost 50-70% of the cost of a new refrigerator.
Can a faulty thermostat simulate a compressor breakdown?
Yes, if the thermostat does not give a signal to turn on, the compressor will be silent, although it is working. Check whether voltage is supplied to the motor terminals when turning the thermostat knob. If there is no voltage, the problem is in the control circuit.