The situation when you open the refrigerator door and see the usual light, but there is room temperature inside, always causes a shock. It seems absurd that the equipment is plugged in, the indicators can light up, and the food begins to spoil. This is a classic scenario, indicating that the electrical circuit powering the lamp is intact, but refrigeration circuit is not doing its job. Understanding the physics of the process helps to quickly find a malfunction.
The light in the chamber comes on from a simple contact that closes when the door is opened, while generating cold requires a complex cycle of compression and expansion of the refrigerant. If the compressor is silent or hums in vain, the problem lies deeper than just a lack of electricity at the outlet. The owner needs to conduct an initial diagnosis to understand whether the problem can be solved on his own or whether a technician needs to be called in with the equipment.
In this article we will analyze the main components responsible for cooling and the symptoms of their failure. We will consider mechanical, electrical and electronic causes of failure. The absence of cold when the backlight is working in 80% of cases indicates a malfunction of the compressor, thermostat or freon leak. Do not rush to throw away the equipment; repairs are often cheaper than buying a new one.
Primary diagnostics: listen and look
The first step should always be a thorough but safe check of the condition of the unit. Go to the refrigerator and listen. Does it make the usual hum? If there is dead silence, although the light is on, this may indicate a broken start relay or a lack of power to the compressor itself. If the motor hums, but clicks and turns off after a few seconds, there is a problem with starting.
Pay attention to the nature of the noise. A uniform hum is a sign of normal operation. An intermittent hum that turns into clicking sounds, or a complete absence of sound after being plugged in requires immediate attention. Also check to see if the compressor housing (usually the black tank at the bottom rear) is overheated. If it is hot, but no cold is produced, the piston may be stuck.
Visual inspection is also important. Check if the door fits tightly. If the seal is worn out or deformed, cold air escapes and the unit cannot reach temperature while idling. Make sure there is nothing preventing the door from closing, such as hanging bags or improperly installed shelves.
Problems with the thermostat and sensors
One of the most common reasons why the compressor does not start is a malfunction thermostat. This mechanical or electronic element is responsible for controlling the temperature inside the chambers. If he “thinks” that there is enough cold, he simply will not signal the motor to turn on. In mechanical models, this is often solved by replacing the part, which a home craftsman can do.
In modern models with a system No Frost and electronic control, air sensors work instead of a thermostat. Their readings are read by the main control module. If the temperature sensor is lying, the refrigerator may “freeze” or, conversely, work without interruption. Diagnosing electronic components requires a multimeter and knowledge of electronics.
⚠️ Attention: Before replacing the thermostat or sensors, be sure to unplug the refrigerator for at least 15 minutes. This is necessary to reset errors in the electronic control module.
Checking the thermostat in mechanical refrigerators is often carried out by elimination or by testing with a tester. If, when you turn the regulator knob, you do not hear a characteristic click and the contacts do not ring, the part is faulty. It is also worth checking the capillary tube of the thermostat for damage.
How to check the thermostat with a multimeter?
Remove the thermostat, set the multimeter to continuity mode. At room temperature the contacts should ring (if the thermostat is normally closed). Place the sensing element in the cold (freezer) - the circuit should break. If there are no changes, the thermostat is faulty.
Faulty compressor and start relay
The heart of the refrigerator is the compressor. It is he who pumps the refrigerant through the system. If the light is on, it means that the phase is supplied to the board or directly to the relay, but the motor does not start. Often the culprit starting relay is a small plastic block placed on the compressor contacts. Inside it there is a posistor or coil, which burn out or stick over time.
If the relay is working properly, but the compressor only hums and knocks out the circuit breaker, the motor-compressor itself may be jammed. This is a serious breakdown. Attempts to “rock” it with a hammer or additional capacitors at home often lead to the final failure of the unit. In this case, the compressor must be replaced and the system recharged.
Symptoms of a compressor malfunction are often accompanied by overheating. If you touch the rear grille and the engine “pot” itself, and they are scalding hot, but there is no cold, this is a bad sign. Also pay attention to the burning smell that may come from a burnt winding.
☑️ Compressor diagnostics
Freon leakage and clogged capillary system
Refrigerant (freon) — this is the lifeblood of the refrigeration system. If the circuit is depressurized, the gas escapes and cooling stops, although the compressor can operate. Leaks often occur at soldered tube joints or due to corrosion of the evaporator. A sign of a leak is a hot condenser (grid at the back) when the engine is running and no cold inside.
Another problem is capillary blockage. A piece of oxide or technical debris may get stuck in the narrow tube where freon throttling occurs. The pressure rises, the compressor hums, but there is no refrigerant circulation. Visually, this is manifested by the fact that the condenser heats up only partially or does not heat up at all.
It is impossible to eliminate a leak or blockage on your own. A vacuum pump, a pressure gauge station and a supply of freon are required. The technician finds the leak, seals it, evacuates the system and fills in new gas in a strictly defined amount.
| Symptom | Probable cause | Required actions |
|---|---|---|
| The compressor does not turn on, silence | The thermostat or relay is faulty | Replacing the thermostat or start relay |
| Buzzing, clicking, does not start | The compressor is stuck or the relay is burned out | Replacing the relay, checking compressor |
| Works constantly, no cold | Freon leak or blockage | Looking for leaks, vacuuming, refilling |
| Frost only at the entrance to the freezer | Clog capillary tube | Purge the system or replace the filter-drier |
Failure of the electronic control module
In modern refrigerators, such as Liebherr, Bosch or Samsung, the whole process is controlled by the “brain” - electronic board. If the triac that controls the compressor burns out, or there is a failure in the firmware, the motor will not receive a command to start. The light bulb is lit because it is powered separately or through another circuit.
Often the electronic module suffers from power surges or moisture ingress (for example, when washing the floor around the refrigerator). Visually, traces of burning, swollen capacitors or oxidized contacts may be visible on the board. Repairing the board requires the qualifications of a radio engineer.
⚠️ Attention: Control modules are very sensitive to humidity. If you flood the floor next to the refrigerator, immediately unplug it and dry the bottom for 2-3 days before turning it back on.
Sometimes a simple reboot helps. Disconnecting from the network for a long time (up to 1 hour) can reset the error in the controller’s memory. If after turning on the refrigerator worked normally, a single software failure may have occurred.
Problems of the No Frost and defrosting system
In refrigerators with the system No Frost cold is produced in the freezer and blown into the main compartment. If the fan does not spin or the air ducts are clogged, the main compartment will be warm, although there may be ice in the freezer. Check if the drainage is clogged and if the fan is working.
A common reason is failure of Defrosting heating element or the defrost timer. If the evaporator becomes covered in ice and does not thaw, the ice coat blocks the channels. The air does not circulate and the refrigerator stops freezing. Visually, this can be seen by disassembling the back wall of the freezer.
Checking the elements of the defrosting system involves checking the continuity of the heating element and the defrost sensor. If the heating element does not ring (break), it does not heat or melt the ice. Replacing the heating element is a simple procedure, but requires complete defrosting of the unit within 24 hours.
When a call to the technician is necessary
Not all breakdowns can be fixed with your own hands. If diagnostics show a freon leak, capillary blockage or mechanical failure of the compressor, you cannot do without special equipment. It is also worth turning to professionals if you are not confident in your skills in working with electricity.
The master will bring with him a vacuum cleaner, scales for refilling freon and a set of tools. He will be able to accurately determine the pressure in the system and the tightness of the circuit. Independent attempts to refuel “by eye” will lead to a quick re-breakdown.
It is worth considering that the complexity of the repair depends on the model. Built-in refrigerators or units with two compressors require more complex diagnostics. If the warranty is still valid, any independent repair will lead to its loss.
Why does the refrigerator hum, but does not freeze?
If a hum is heard, it means the compressor is trying to work. Reasons: 1. Jammed compressor (motor hums, but the shaft does not spin). 2. Freon leak (the compressor is running empty). 3. Capillary tube clogged. 4. Malfunction of the starting relay, which cannot start the rotor.
Is it possible to temporarily use the refrigerator if it does not freeze?
It is possible to use it as a storage cabinet, but it is not recommended to keep it turned on. If there is no cold, the compressor will run continuously, trying to gain temperature, which will cause it to overheat and burn out. It is better to turn off the unit, defrost and dry it before the technician arrives.
How long should you wait after transportation before turning it on?
If the refrigerator was transported lying down, oil from the compressor could leak into the circuit. It is necessary to let it stand vertically for at least 4-8 hours (preferably a day) before turning it on for the first time. If you turn it on right away, water hammer and compressor failure may occur.
What to do if an ice coat has formed in the refrigerator?
You need to completely defrost the refrigerator. Unplug it, open the doors and leave it for at least 12-24 hours. Do not use a hair dryer or hot water to speed it up - this may damage the plastic and evaporator tubes. After defrosting, wipe dry and turn on.