The situation when a display refrigerator stops maintaining the set temperature always takes you by surprise, especially at the height of the trading day. Products begin to deteriorate, and revenue falls due to the inability to sell goods of adequate quality. Business owners and technicians need to immediately respond to such failures in order to minimize financial losses.
There can be many reasons why equipment fails: from trivial contamination of the capacitor to serious refrigerant leaks. Understanding how your refrigeration machine works helps you isolate the problem faster. In this article we will analyze the main malfunctions, methods for identifying them and ways to eliminate them.
It is worth considering that modern models are equipped with complex electronics that can block the operation of the compressor at the slightest sensor failure. Therefore, diagnosis must be comprehensive and consistent. Even minor changes in the sound of operation or the appearance of the unit components cannot be ignored.
⚠️ Attention: If you detect a burning smell or sparking, immediately turn off the power to the equipment. Further operation in this condition may lead to fire or electric shock.
Primary diagnosis and external signs of malfunction
Before disassembling the unit, it is necessary to conduct a thorough external inspection. Often the answer to the question why cooling does not work lies in the obvious. Check if the power indicator is on and if you can hear the characteristic hum of the motor. If the compressor is silent, the problem may be in the electrical circuit or the start relay.
Pay attention to the temperature inside the display case. If it rises slowly but the compressor runs continuously, this may indicate a loss of circuit tightness. In the case when the motor turns on and immediately turns off, the thermal protection relay is probably triggered due to overheating.
Visually assess the condition of the capacitor (grid at the back or bottom). If it is covered with a thick layer of dust and fluff, heat transfer is impaired. This is the most common cause of overheating and subsequent system shutdown. Regular cleaning of this unit is an obligatory part preventive maintenance.
Problems with the compressor and start relay
The heart of any refrigeration machine is the compressor. If this unit is faulty, refrigerant circulation will not be possible. The engine may hum but not start, or it may start for a split second and click. Such symptoms often indicate a failure of the starting relay or the windings of the motor itself.
In some cases, the compressor works, but does not create the necessary pressure. This can occur when the valve group or piston system wears out. You can determine low performance by touching the discharge pipe: it should be hot. If it is barely warm when the engine is running, the compressor “does not pump.”
- 🔌 Open circuit: Check the integrity of the supply wires and contacts.
- 🔥 Overheating: The thermal relay opens the circuit when the permissible temperature of the windings is exceeded.
- ⚙️ Mechanical wear: A knock or grinding sound inside the compressor housing indicates destruction of internal parts.
Replacing a compressor is a complex procedure that requires evacuation of the system and charging with freon. It is almost impossible to do this work independently without special equipment. It is better to contact a specialized service to replace the unit.
How to check the starting relay?
Disconnect the relay from the compressor and shake it. If a ringing sound is heard inside (as from broken ceramics), it means that the posistor or contacts are damaged and require replacement.
Freon leakage and failure of the circuit tightness
One of the most common reasons for the lack of cold is a refrigerant leak. Freon circulates in a closed circuit, and if a microcrack has formed somewhere, the gas gradually comes out. As a result, the pressure in the system drops and the evaporator stops absorbing heat from the chamber.
Leaks are often located in areas of metal corrosion, for example, in foamed sections of pipelines or in soldering areas. Sometimes the cause is mechanical damage to the evaporator due to careless defrosting or cleaning the display case. It is difficult to visually find a leak; the use of a leak detector or soap solution is often required.
If there is little freon left in the system, the compressor will work non-stop, trying to gain temperature. This leads to rapid wear and overheating. It is important to notice in time that the refrigerator has stopped freezingin order to prevent failure of expensive components.
⚠️ Attention: Freon itself has no odor, but if it leaks in the presence of oil, a specific chemical odor may appear. Do not inhale refrigerant vapors, it is harmful to health.
Malfunctions of the thermostat and temperature sensors
Electronics controls the operation of the refrigerator based on sensor readings. If thermostat or the temperature sensor (thermistor) fails, the controller may “think” that the chamber is already cold and does not turn on the compressor. Or, on the contrary, keep it on all the time.
Mechanical models use a capillary tube with a bellows. If this tube is damaged or the bellows loses its tightness, the thermostat stops responding to temperature changes. In electronic systems, most often the thermistor itself fails, changing its resistance.
Diagnostics of sensors is carried out using a multimeter. It is necessary to measure the resistance at different temperatures and compare the readings with the table for a specific model. Deviation of values indicates the need to replace the element.
| Sensor type | Failure symptom | Check method |
|---|---|---|
| Mechanical thermostat | The compressor does not turn on or does not turns off | Ringing of contacts when temperature changes |
| Electronic thermistor | Error on the display, incorrect temperature | Measuring resistance with a multimeter |
| Defrost sensor | Ice build-up, lack of cold | Checking the circuit in defrost mode |
Replacing the sensor usually does not take much time and does not require opening the freon circuit. This is one of the most affordable types of repairs, which can often be done independently if you have basic skills.
Clogged capillary tube and filter drier
Not only freon circulates inside the refrigeration system, but also special compressor oil. Over time, oxidation products, moisture, or debris can build up in the system, causing a clog to form. Most often, a blockage forms in the narrowest place - a capillary tube or a filter-drier.
Signs of a blockage are: a working compressor, but a cold condenser (or its heating only at the beginning) and a lack of cooling in the chamber. Sometimes you can hear gurgling sounds when the engine stops, which indicates the presence of fluid in the circuit that cannot circulate.
To eliminate this problem, professional cleaning of the system with nitrogen under pressure is required. Often it is necessary to replace the filter drier and re-evacuate and recharge with refrigerant. It is extremely difficult to eliminate a deep blockage without equipment.
☑️ Actions if the system is clogged
Problems with the defrost system (for No Frost models)
If your display refrigerator is equipped with a No Frost system, the lack of cold may be caused by a failure in the evaporator defrost cycle. The defrost heating element, timer or defrost sensor may fail, causing the evaporator to become coated with ice and block the air flow.
The fan, which is supposed to drive cold air into the chamber, may become jammed with ice or stop working due to a motor failure. In this case, the compressor works, freon circulates, but the coolant does not enter the commercial volume of the display case.
It is necessary to remove the back wall inside the chamber and inspect the evaporator. If it is covered with a thick crust of ice and the fan is not running, then the defrost system is not functioning. It is necessary to check the heating element circuit and sensors.
⚠️ Attention: Do not try to break off the ice with a knife or sharp objects. Damage to the evaporator tubes will lead to an immediate leak of freon and costly repairs.
Frequently asked questions and answers (FAQ)
Why does the refrigerator hum, but does not freeze?
Most likely, there is a freon leak or a blockage in the capillary system. The compressor idles, trying to build up pressure, but the refrigerant is not circulating. It is also possible that the compressor itself is malfunctioning and does not develop the required power.
Is it possible to operate a refrigerator with a faulty thermostat?
It is highly not recommended. If the thermostat does not turn off the compressor, food may freeze and the motor itself will burn out from overload. If he does not turn on the motor, the food will spoil. The element needs to be replaced.
How often should the display condenser be cleaned?
In a store with high traffic, cleaning should be carried out at least once every 3-4 months. Dust significantly impairs heat transfer, causing the compressor to work longer and consume more electricity.
What to do if the display case stops freezing after defrosting?
If after complete defrosting (24 hours) the cold does not appear, there may be moisture left in the system that has frozen in the capillary, or the trigger mechanism has failed. Try turning the device on and off the outlet several times at intervals of 5 minutes. If it doesn’t help, call a specialist.