A sudden stop of the refrigerator is always stressful, because food supplies are at risk. Often the reason for equipment silence is the failure of the motor-compressor, which is the heart of the entire cooling system. Before calling a technician or buying a new unit, it is necessary to carry out initial diagnostics to understand whether the problem really lies in the engine or whether it is enough to replace a small part.
Self-check compressor allows you to save a significant amount and time, since in many cases the fault lies in the starting relay or thermostat, and the motor itself is working. However, if the diagnostics show a break or inter-turn short circuit of the windings, then repairing the engine becomes economically impractical and will require its replacement. It is important to understand that working with electrical components requires compliance with safety precautions and care.
In this article we will analyze in detail the algorithm of actions, the necessary tools and methods for checking various motor components. You will learn to distinguish a mechanical knock from an electrical breakdown and understand when the unit can still be saved and when it must be disposed of. Diagnostics this is the first and most important step to restoring the performance of your equipment.
Primary visual diagnosis and analysis of symptoms
Before picking up a multimeter, it is necessary to conduct a thorough external inspection and analyze the behavior of the refrigerator in the last hours of operation. Often the nature of the sound or its absence can say a lot about the condition motor-compressor. If, when plugged in, a quiet hum is heard, which abruptly ends after a few seconds, this may indicate a jammed piston group or a malfunction of the starting mechanism.
Pay attention to the temperature of the motor housing. If the unit turns on, hums, but does not start, and the motor housing becomes hot, this is an alarming signal. During normal operation, the compressor heats up, but should not become too hot to touch. It is also worth inspecting the back wall of the refrigerator for oily stains.
⚠️ Attention: The presence of oil around the compressor or on the floor under the refrigerator often indicates a depressurization of the system or a crack in the motor housing. You cannot operate such a unit - this can lead to complete release of freon and combustion of the windings.
Visually assess the integrity of the wires going to the motor. Melted insulation or blackened contacts indicate overheating and a possible short circuit. If there are no external signs of failure, and the refrigerator simply does not turn on, we move on to a deeper check of the electrical part.
Necessary tools for checking the motor
For high-quality diagnostics, you will need a minimum set of tools, which can be found in many home craftsmen. The main device will be multimeter (tester), which allows you to measure resistance and test circuits. Without this device, checking the windings for open or short circuit is impossible.
In addition to the measuring device, prepare the following tools:
- 🔧 Screwdrivers (Phillips and flat) for removing the protective casing and terminals.
- ✂️ Pliers or pliers for carefully removing terminals.
- 🧹 Sandpaper or alcohol to clean contacts from oxides.
- 🔦 Flashlight for better illumination of the inside of the engine compartment.
Make sure that The multimeter is working properly and has charged batteries. Verification start relay may require a separate test, but the basic set remains the same. If you do not have experience working with electrical appliances, it is better to enlist the help of a person who understands electrical equipment.
Checking the integrity of the motor windings with a multimeter
The most reliable way to determine the condition of the motor is to test the continuity of the windings. To access the contacts, you need to remove the rear protective cover of the compressor (usually it is plastic and secured with latches or screws). Below it you will see three terminals covered by the start relay.
Carefully remove the start relay and start capacitor to free the contacts. On most modern compressors, the terminals are arranged in a triangle. You need to measure the resistance between each pair of pins. Normal resistance values for a working engine are usually in the range from 10 to 30 Ohms for the working winding and slightly higher for the starting winding.
During the measurement process, pay attention to the readings of the device:
- 📉 If the device shows infinity (break), it means that one of the windings has burned out or the wire inside the case has been broken.
- 📈 If the resistance is close to zero, this indicates a short circuit of the turns.
- ⚡ If the device shows resistance, but when you touch the motor housing the arrow or numbers change, it means there is a breakdown to the housing (short to ground).
For example, for high-power two-compressor models, the values may differ from low-power ones single-chamber. The main thing is the absence of a break or short circuit to the housing.
What to do if the resistance values differ greatly?
If the difference between the winding resistances exceeds 50%, this may indicate an interturn short circuit. Such an engine will operate unstably and quickly overheat.
After measurements, compare the data obtained with the table values for your type of compressor. If at least one parameter is outside the normal range, the engine is most likely faulty.
Testing the start relay and thermostat
Often the cause of a non-working refrigerator is not the motor itself, but its “retinue” - the start relay and thermostat. The starting relay is responsible for providing an impulse to start the engine. If it is stuck or burnt out, the motor will hum, but will not start, after which the thermal protection will work.
The relay can be checked visually and using a multimeter. Shake the relay: if a ringing sound is heard inside, it means the mechanism is destroyed. Also check the contacts for carbon deposits. The thermostat is checked by continuity: at room temperature its contacts should be closed (resistance close to 0).
For easy comparison of symptoms and possible causes, use the following table:
| Symptom | Probable cause | Action |
|---|---|---|
| Silence, no hum | Open circuit, thermostat, relay | Ring the power circuit |
| Hum for 5-10 seconds, then click | Stuck, start relay | Check the relay, try to start it directly |
| The machine in the panel is triggered | Short circuit in the windings | Measure the resistance for breakdown of the housing |
| The motor is hot, but does not work | Interturn short circuit | Replacing the compressor |
If the check shows that the relay and thermostat are working, and the motor windings are normal, but the motor still does not start, there may be a problem in the mechanical part or a voltage drop in the network. In some cases, it is necessary to replace the starting device with a similar one.
Direct start of the compressor without a relay
There is a method for checking the performance of the motor by directly connecting to the network, bypassing the start relay and thermostat. This method allows you to rule out a malfunction of the control electronics and check whether the engine is physically able to start. However, this method requires caution.
For direct starting, it is necessary to apply 220V voltage directly to the working winding. Typically these are pins 1 and 2 (or 1 and 3, depending on the marking) on the compressor block. The starting winding must be short-circuited at the moment the voltage is applied to simulate the operation of the starting relay.
⚠️ Attention: Direct starting is dangerous due to electric shock and the risk of damaging the compressor if the phasing is connected incorrectly. Do not hold onto metal parts of the engine while applying voltage!
If, when voltage is applied, the engine starts confidently and runs smoothly, without making any extraneous sounds, then the mechanical and electrical parts of the motor are working properly. In this case, the problem lies in the control system (relay, thermostat, control module). If the motor hums, jerks or knocks out plugs, there is a serious malfunction of the unit itself.
☑️ Direct start algorithm
After a successful start, let the motor run for several minutes, monitoring the outlet pressure (if there is a pressure gauge) and temperature. A sharp increase in pressure or lack of suction may indicate a loss of compression.
Diagnosis of mechanical faults and loss of compression
The electrical health of the engine does not guarantee its normal operation. The mechanical parts - pistons, valves and connecting rods - can be worn out. The simplest test for loss of compression is to check the air intake and air discharge. Disconnect the capillary tube and return tube from the compressor (after unsoldering or cutting them off).
When turned on, a working compressor should actively suck in air at the inlet and forcefully blow it out at the outlet. If you put your finger to the suction tube, but it does not stick, or the stream at the outlet is barely felt, then the valve group is faulty. In such cases, they say that the compressor “does not hold pressure.”
The causes of mechanical failure may be the following:
- 🔨 Wear of the piston group due to long-term operation.
- 💧 Moisture entering the system, causing corrosion and jamming.
- 🔩 Destruction of the connecting rod and piston group due to water hammer (liquid freon entering the cylinder).
It is almost impossible to restore the mechanical part of the compressor at home. It requires complete disassembly and replacement of valves and pistons, which requires special equipment and skills. Therefore, if a mechanical fault is confirmed, the engine must be replaced.
It is also worth listening to the sound of the running motor. Metallic knocking, clanging or vibration transmitted to the refrigerator body indicate broken bearings or shaft misalignment.
Frequently asked questions about compressor diagnostics
Is it possible to repair a burnt-out compressor or does it need replacement?
B In 95% of cases when the windings burn out or mechanical jamming, the compressor is easier to replace than to repair. Rewinding the motor requires factory conditions, and mechanical repairs often exceed the cost of a new unit. For older models of refrigerators, repair may not be practical.
Why may a new compressor not start after replacement?
The reasons may be incorrect installation of the start relay, a malfunction of the thermostat, lack of freon (dry running protection) or low voltage in the network. It is also important to check whether the system is sealed correctly, since high condensation pressure can block starting.
How to distinguish a compressor malfunction from a freon leak?
If there is a freon leak, the compressor usually runs constantly without turning off, but the refrigerator does not freeze. If the engine does not start at all or the automatic switch breaks, the problem is most likely in the electrics or mechanics of the engine itself, and not in the refrigerant.
Is it dangerous to change the compressor yourself?
Replacing the compressor requires soldering copper pipes, evacuating the system and accurately filling with freon. Without special equipment (vacuum pump, pressure gauge station, scales) it is impossible to perform this work efficiently. Errors lead to rapid failure of the new motor.