A sudden stop of a refrigeration unit or, conversely, its continuous operation without any visible result is always an alarming signal for the owner of household appliances. Most often, the cause of such anomalies is the heart of the cooling system, and the question of how to determine a faulty refrigerator compressor becomes paramount. Understanding the basic principles of motor operation allows you not only to save on calling a technician for simple diagnostics, but also to prevent damage to products in time.
A compressor is a piston or linear pump that drives the refrigerant through a closed circuit, creating the necessary pressure for condensation and evaporation of freon. If this mechanism fails, the cooling cycle is interrupted and the temperature in the chambers begins to rise. However, the lack of cold does not always mean the death of the engine; sometimes the problem lies in adjacent elements, such as a thermostat or start relay.
In this article we will analyze in detail the symptoms that indicate critical wear or breakdown of the unit, and learn to distinguish them from less serious failures. You will learn how to conduct an initial visual and acoustic assessment, as well as what measurements need to be taken with a multimeter for an accurate diagnosis.
Primary diagnosis: hearing and tactile sensations
The easiest way to suspect something is wrong is to listen to the sounds that the equipment makes during operation. A working modern refrigerator operates almost silently, emitting only a slight hum when turned on. If you hear loud clicks, knocking, metallic clanging or a hum that turns into vibration, these are direct signs of mechanical problems inside the motor housing.
Pay attention to the nature of the noise. Humming without subsequent starting often indicates that the motor is trying to start, but cannot turn the shaft. Clicks s periodicity of several minutes indicates the activation of a thermal protection relay, which turns off the power due to overheating of the windings or jamming of the mechanism.
⚠️ Attention: If, when you try to start, you hear a loud bang or smell a burning smell, immediately disconnect the device from the power supply. Further attempts to turn on may lead to a fire in the wiring or complete failure of the device.
Tactile testing is also an important step. During normal operation, the compressor housing should be warm, but not scalding. If you feel intense heat when you touch the back wall (where the motor is located), this indicates overheating. The reason could be a malfunction of the motor itself, or problems with the ventilation or heat removal system.
Visual signs and analysis of the cycle operation
Visual inspection allows you to identify a number of problems without the use of tools. First of all, check whether the refrigerator operates in normal cyclic mode. A normal cycle involves periodically turning the engine on and off. If the motor hums continuously 24 hours a day, trying to reach the set temperature, but does not turn off, this is a sure sign of loss of performance.
Loss of performance is often associated with the exhaustion of the piston group resource. In this case, the compressor works, freon circulates, but the pressure in the system is not enough for effective cooling. Inverter compressors in such cases, they may not hum constantly, but operate at elevated speeds, which is also a sign of a malfunction.
Inspect the tubes and the housing itself for traces of oil. Oil is used to lubricate the rubbing parts inside the engine, and its presence outside (especially in the lower part of the unit or on the pipes) indicates depressurization. This may be a consequence of corrosion or mechanical damage, which inevitably leads to freon leakage and moisture entering the system.
Checking the starting relay and electrical circuit
Before sinning on the motor itself, it is necessary to eliminate the possibility of the starting relay breaking. This small element is responsible for supplying a starting pulse to the motor winding. If the relay is faulty, the compressor will hum, but will not start, because it does not receive the necessary push to rotate the shaft.
To check the relay, it must be removed and shaken. If a knocking noise is heard inside, it means the core is broken or displaced and the part needs to be replaced. It is also worth inspecting the contacts for oxidation or carbon deposits. Often the problem is solved by installing a new relay, the cost of which is disproportionately lower than the cost of replacing the compressor.
Checking the electrical circuit includes inspecting the power cable and plugs. Make sure the mains voltage is stable. Voltage surges could damage the control electronics, which is why the start signal simply does not reach the engine. In modern models with electronic control, diagnostics require connection to the service port.
Symptoms of a faulty starting relay
If the relay is working properly, but the compressor does not start, the problem may be a broken winding. However, if after replacing the relay the motor started working, then the reason was precisely in the starter. Do not ignore this stage, since frequently replacing burnt-out compressors without checking the relay is a common mistake.
Diagnostics with a multimeter: resistance measurements
The most accurate testing method is to use a multimeter. This tool allows you to measure the resistance of the motor windings and determine the presence of breaks or short circuits. To carry out diagnostics, it is necessary to remove the protective casing and gain access to the compressor contacts.
The measurement process is as follows:
- 🔌 Disconnect the refrigerator from the mains and remove the back cover.
- 🔧 Remove the start relay to free the three motor contact pins.
- 📏 Switch the multimeter to resistance measurement mode (Ohm).
- ⚡ Ring pairs of contacts: common with the worker, common with the starting one, working with the starting one.
In a working engine, the resistance between the contacts should be in a certain range (usually from 10 to 60 Ohms, depending on the model). If the device shows infinity (one on the screen), it means in the winding break. If the resistance is close to zero, it happened short circuit. In both cases, the compressor must be replaced.
It is also important to check the breakdown on the housing. One multimeter probe is applied to any contact, and the second is applied to the stripped metal part of the case or copper tube. The device should show infinity. If there is at least some resistance value, it means that the winding insulation is broken, and operating such a unit is deadly.
☑️ Diagnostic procedure with a multimeter
Table of symptoms of malfunctions
To systematize the obtained data, it is convenient to use a pivot table. It will help you compare the observed symptoms with probable causes and decide on further actions. Remember that a combination of several signs increases the likelihood of a serious breakdown.
| Symptom | Probable cause | Necessary actions | Difficulty of repair |
|---|---|---|---|
| Buzzes, but does not starts | Starting relay is faulty or jammed | Replacement of relay, attempt to wedge | Low / High |
| Works without stopping | Freon leakage, piston wear | Search for leaks, replace the compressor | High |
| The housing gets very hot | Overload, poor ventilation | Cleaning the condenser, replacement motor | Medium |
| A knock is heard inside | Destruction of valves or suspension | Replacement of the compressor | High |
| Knocks out the machine in the panel | Short circuit of the winding | Urgent engine replacement | High |
Analysis of the table shows that most serious symptoms, such as constant work or knocking noises require qualified intervention. You can replace only the relay yourself or eliminate external factors of overheating, but replacing the motor itself requires evacuation of the system and refilling with freon.
⚠️ Attention: It is strictly not recommended to open the sealed circuit of the cooling system yourself without special equipment. The release of freon into the atmosphere is harmful, and moisture entering the system will lead to rapid failure of the new compressor.
Mechanical damage and jamming
Compressor jamming is a condition when the piston or crank mechanism is physically unable to move. This often occurs due to oil burnout, moisture entering the system (which causes acid reactions) or prolonged downtime of equipment. In this state, the motor shaft is blocked.
When you try to start a jammed motor, the current in the windings increases sharply, which leads to instant heating and tripping of the protection. If you do not stop the process, the windings will burn out. There is a “wedging” method by applying increased voltage, but it is effective only in the initial stage and requires experience.
Mechanical damage can also be caused by transportation. If the refrigerator was transported lying down without observing the settling time intervals, oil could get into the circuit, and shocks could dislodge the internal components. Horizontal transportation without settling in a vertical position for 2-4 hours often leads to water hammer at the first start.
FAQ: Frequently asked questions
Is it possible to repair a refrigerator compressor yourself?
Full repairs (replacing valves, pistons) at home are impossible, since sealed welding and vacuuming. You can independently replace only the start relay or the entire unit itself, but you still need a technician to fill with freon.
How much does it cost to replace a compressor?
The cost is the sum of the price of a new engine, the cost of a technician’s work, and the price for refilling with refrigerant. On average, this ranges from 50% to 80% of the cost of a new refrigerator, so it is often more advisable to buy new equipment.
Why does the compressor turn on and then immediately turn off?
This is a thermal protection relay triggered. Reasons: motor jamming, faulty start relay, short circuit in the windings or critically low voltage in the network.
Is it dangerous to use a refrigerator with a humming compressor?
If the humming is accompanied by overheating of the housing or a burning smell, use is dangerous due to the risk of fire. If it just hums louder than usual, but gets cold, this is a matter of comfort and the service life of the equipment.
How to extend the life of a compressor?
Regularly defrost the refrigerator, do not place it close to the wall for ventilation, avoid sudden power surges and do not load hot foods into the chamber.