The situation when the top shelf in the refrigerator suddenly stops freezing often takes you by surprise. Food in the main compartment begins to spoil, and ice may melt in the freezer compartment. This is a classic symptom of poor refrigerant circulation or problems with the defrost system. Understanding the physics of the cooling process will help you quickly determine the essence of the breakdown.
Refrigeration units operate on the principle of forced or natural circulation of freon. If the upper part, which is usually the evaporator or receives cold directly from it, has become warm, it means that the cold transmission chain is broken. Malfunction can be hidden either in a banal blockage or in the failure of the compressor.
In this article we will analyze in detail the main reasons, why the top part of the refrigerator is not cooling, and we will tell you what you can do yourself, and when it is better to call a professional. Ignoring the problem at an early stage can lead to complete damage to the products and expensive repairs.
Seal failure and freon leak
One of the most common reasons for the lack of cold in the upper compartment is a refrigerant leak. Freon is a working fluid that circulates through a system of tubes, picking up heat. If a hole is formed in the circuit, the gas escapes and the pressure drops. As a result, the compressor circulates air, but there is no cold.
Most often, leaks occur in places where tubes are welded or in the foamed part of the housing, where the metal comes into contact with an aggressive environment. You may notice that compressor it runs almost non-stop, trying to get the temperature up, but the top shelves remain warm. In this case, the condenser grille at the back may be barely warm or cold.
Sometimes a leak can be detected visually or audibly if it occurs in an accessible place, for example, near the door. However, in most cases the use of a leak detector is required. Self-refilling with freon is impossible without special equipment and skills in vacuuming the system.
⚠️ Attention: If you hear hissing or whistling from the back of the refrigerator, immediately unplug the device. This may be a sign of depressurization of the system under pressure.
Diagnostics of a leak requires checking the pressure in the system. The technician connects a pressure gauge station and nitrogen to find the location of the damage. After eliminating the hole and replacing the filter-drier, evacuation is carried out and a new portion of refrigerant is charged.
Malfunctions of the No Frost and defrost system
In refrigerators with the system No Frost cold is produced in the evaporator, which is usually located in the upper part or behind the rear wall of the freezer. The fan blows this cold throughout all the chambers. If the top does not cool, there may be a malfunction in the defrost cycle.
Snow build-up on the evaporator is blocking airflow. The fan continues to hum, but the air simply cannot pass through the ice shell to the food. This often happens when there is a breakdown Defrost heating element, timer or defrost sensor.
To test this hypothesis, you need to defrost the refrigerator completely. Leave the doors open for at least 24 hours. If after turning on the cold appears and lasts for several days, and then disappears again, the problem is definitely in the defrosting system.
Why does ice block the cold?
The ice crust on the evaporator works as a heat insulator. The freon inside the tubes boils and cools the walls, but the ice prevents the cold from moving into the chamber. In addition, ice blocks the channels through which the fan should blow cold air.
Replacing a heating element or sensor is a technically simple procedure, but requires disassembling the inside of the freezer. It is important to correctly select the parameters of the replaced elements so that the defrost cycle proceeds correctly.
Clogged capillary tube
The capillary tube is a narrow channel through which liquid freon is supplied to the evaporator. Over time, oil oxidation products or moisture can accumulate in the system, which turns into an ice plug. This phenomenon is called clogging.
When the capillary is clogged, the refrigerant circulation is disrupted. Freon cannot get into the evaporator in sufficient quantity, so the upper part of the refrigerator, where the evaporator is usually located, stops cooling. In this case, the compressor may operate jerkily or with increased noise.
The blockage can be determined by a characteristic sign: the condenser (grid at the back) is only partially heated, and the tube at the outlet of the compressor may be hot, while at the inlet to the evaporator it is cold. Sometimes “pushing” the system with nitrogen under high pressure helps.
It is almost impossible to eliminate a serious blockage at home. The system requires opening, purging with nitrogen, replacing the filter drier and refilling. Attempts to break the plug without vacuuming can drive moisture deeper into the system.
Problems with the fan and air distribution
If your refrigerator is equipped with a forced circulation system, then the fan is responsible for air movement. Its malfunction is a common reason why the cold does not reach the top of the refrigerator compartment. The fan may simply stop due to wear of the bearings or breakage of the winding.
You can check the operation of the fan by opening the freezer door (in some models you need to press a special lever that simulates a closed door). If there is no noise from the motor and there is no ice on the blades, it is most likely burned out.
Also, air may not flow due to blockage of the air channels. This happens when food is packaged in large bags and the circulation holes are tightly plugged. In such cases, it is enough just to correctly place the products.
It is important to keep the fan blades clean. Dust and grease can stick to them, which creates an imbalance and increases the load on the engine, leading to its premature failure.
Failures in the operation of the thermostat and electronics
The thermostat (thermostat) or electronic control module is responsible for maintaining the temperature. If the temperature sensor located in the upper part fails or gives incorrect readings, the “brains” of the refrigerator may think that it is already cold there.
As a result, the compressor does not turn on or turns off too early, without having time to cool the chamber. In models with electronic control, failures in the control board often occur, especially if the voltage in the network fluctuates.
Thermostat diagnostics are carried out using a multimeter: the resistance of the sensor is checked at different temperatures. Electronic modules require more complex testing, often by excluding other faults.
| Symptom | Possible cause | Nature of compressor operation |
|---|---|---|
| Top is warm, bottom is cold | Clogging capillary | Works for a long time, hums |
| Complete absence of cold | Freon leakage | Works constantly |
| There is cold, but weak | Fan is faulty | Works normally |
| Temperature fluctuates | Thermostat is faulty | Frequent on/off |
Replacement The thermostat is one of the simplest procedures. It is better to entrust the electronic module to professionals, since reflashing or soldering of components will be required.
Wear of the compressor and motor
The compressor is the heart of the refrigerator. If it is worn out, it may not create enough pressure to pump freon throughout the system. In such cases, freon circulates, but only in the initial part of the circuit, without reaching the evaporator in the upper part.
Signs of a weak compressor are: a quiet hum, lack of vibration on the housing, a hot motor housing with a cold condenser grille. The motor may try to start, click the start relay and stall.
In some cases, replacing the start-up relay helps. This is an inexpensive part that is often the first to fail. If the problem is in the mechanical part of the compressor (valves), it will need to be replaced.
⚠️ Attention: Replacing a compressor is a complex operation that requires soldering pipes and working with refrigerant. It is extremely difficult to independently perform it efficiently without equipment.
Modern inverter compressors can only be diagnosed using a special tester. It is impossible to check their performance with a regular test of the windings.
Rules of operation and placement of products
Sometimes the reason for a warm top is trivial - a violation of the rules of operation. If you put a large amount of warm food in the refrigerator, the system may not be able to cope with the heat load. Also, the cold will not circulate if the shelves are filled to capacity.
Check the rubber seals on the doors. If they do not fit tightly, warm air enters the chamber, and the moisture from it actively freezes on the evaporator, blocking the cold. Wipe the rubber bands and check their elasticity.
☑️ Quick diagnostics of the refrigerator
Maintaining a distance between the products and the back wall ensures proper airflow. Do not place pots of soup directly next to the cold air outlet.
Frequently asked questions (FAQ)
Is it possible to operate the refrigerator if the top part does not freeze?
Short-term operation is possible, but undesirable. The compressor will work hard, trying to gain temperature, which will lead to overheating and eventual breakdown. The food in the upper compartment will spoil.
How long does it take to defrost the refrigerator to check?
A minimum of 24 hours is required to completely defrost the evaporator and remove the ice plug. It is better to leave the refrigerator turned off with the doors open for a day so that all the moisture has time to evaporate.
Why did the cold appear after defrosting, but disappeared again a week later?
This is a sure sign of a malfunction of the defrosting system (heating element, timer or sensor). Ice has again accumulated on the evaporator and blocked the channels. The faulty element of the No Frost system needs to be replaced.
Can moving the refrigerator away from the battery help?
Yes, if the refrigerator is located next to a heat source, the efficiency of condensation decreases. The compressor runs longer but does not cool properly. Maintain a gap at the back wall.