There are several methods for refrigerator repair.
(1) Inquiry and inspection method
The inquiry and inspection method is the most basic method for repairing the refrigerator control system. In fact, this method is also the most easily ignored by beginners and maintenance personnel. After receiving the faulty machine, they did not patiently ask the user, and did not distinguish whether it was a real fault or a false fault, and then began to disassemble it aggressively. Sometimes, not only could the fault not be eliminated quickly, but the fault could easily be expanded. This not only wastes time but also damages the reputation of both the individual and the maintenance department. Therefore, before repair, it is very important to carefully ask the user whether the machine has been repaired, the characteristics of the fault, and how the fault was caused. The repair of many faults can be done with half the effort. For example, when troubleshooting a compressor non-stop fault, if the user says that the refrigerator's cooling effect is poor, it means that the fault is caused by a leak in the refrigeration system or an abnormality in the compressor; if the temperature is too low (such as freezing in the refrigerator compartment), it means that The fault is caused by the thermostat's contacts failing to open.
(2) Visual inspection method
Visual inspection method is the most basic method for repairing refrigerators. It is a maintenance method that determines the fault location through one look, two listens, three touches, and four smells. This method can be used to make a preliminary judgment on the fault location during maintenance.
1. Look
Looking is a maintenance method to find the fault location and cause of the fault through observation. Next, judge the fault location based on the characteristics of different parts.
When troubleshooting the problem that the light does not light up, you can first check whether the filament of the light is burned out. If it burns out, it means that the light is damaged. When troubleshooting the problem that the compressor does not start, check the starter and overload protector. Are they falling off or damaged? If so, it means they are damaged. When the compressor is running normally, if there is no frost on the surface of the evaporator, the frost is not solid or the frost is uneven, it means the refrigeration system is working abnormally.
The evaporator in the cold room of the direct-cooled double-door refrigerator is always full of frost, instead of alternating between defrost and frost. You should check whether the door seal is normal. If the door seal is normal, it is mostly due to the temperature problem. The controller is abnormal. If the indirect cooling refrigerator is not cooling normally, check whether the fan blades are frozen. If so, the automatic frost circuit is abnormal. If the freezer is not frosted but icy, it means the compressor has been running for too long and the thermostat should be checked.
After filling the refrigerator with refrigerant, if frost is found on the return pipe, it means that too much refrigerant has been added. When troubleshooting the problem of no cooling or poor cooling, you should first check the condenser and compressor. Is there any oil stain on the welding point with the copper pipe? If so, it means there is leakage there. In addition, when troubleshooting a non-cooling failure caused by manual defrosting, you should first check whether the evaporator has been scratched by a tool, etc. After filling the refrigerator with refrigerant, let it operate. If there is a lot of frost on the return pipe of the compressor, it means too much refrigerant has been added. If the filter dryer is frosted, it is usually due to incomplete evacuation during maintenance, which may lead to ice blockage due to excessive moisture. The connection between the dry filter and the capillary tube is frosted, indicating that there is a dirty blockage here.
After pressurizing the refrigeration system of the refrigerator, you can determine whether there is a leak in the refrigeration system by checking whether the reading of the pressure gauge changes.
2. Listening
Listening is the maintenance method to find the fault location and cause of the fault through listening with the ears:
When checking the non-cooling fault, it is the refrigerator After powering on, if you cannot hear the "clicking" sound from the heavy hammer starter, it means that the power supply system, starter or compressor is abnormal; if you hear the "clicking" sound from the starter, but The compressor made a loud "buzzing" sound, and soon the overload protector made a "click" sound, indicating that the mains voltage, starter or refrigeration system abnormality caused the compressor to overheat, causing the overload protector to operate. Of course, an abnormality in the compressor will also cause this fault; if you hear an abnormal sound from the compressor after the compressor is started, it means that the spring in the compressor is decoupled, broken or stretched; if the compressor has just stopped and you hear something inside the casing An obvious sound of air leakage indicates abnormality in the valve; if the compressor is operating normally and there is no "hissing" sound of air flow in the evaporator, it indicates that the refrigerant has seriously leaked.
When servicing a fault that can cool but the cooling effect is not good, if there is a sound of jetting when the compressor is running or a sound of air leaking when it is stopped, it means that the mechanical system in the compressor is damaged; if the evaporator A cry of "Qing!" or intermittent puffing sound indicates that the pipeline is blocked.
The refrigeration is normal, but there is a banging sound, which is mostly caused by the water box, condenser, filter and other components being loose.
3. Touch
Touch is a maintenance method to find the fault location and cause of the fault by touching it with your hands.
When troubleshooting a non-cooling fault, if the overload protector operates shortly after the compressor is started and the temperature of the compressor is high, it indicates that the compressor is working abnormally. When troubleshooting a noisy fault, if the filter is noisy when touching Significantly reduced, indicating that the capillary tube is vibrating and needs to be re-fixed. If the noise drops significantly when touching the water box, it indicates that the water box is loose. If the noise drops significantly when touching the condenser, it indicates that the condenser is loose. In addition, the refrigeration effect must be inspected. In the case of poor failure, if the condenser temperature is locally overheated and other parts are not hot, it means that the system is not properly evacuated during maintenance; if the hot area is small but the temperature changes uniformly, it means that the refrigerant is insufficient. When troubleshooting poor cooling effect, you can check whether the door seal is deformed by touching the door seal.
4. Smell
Smell is a maintenance method to find the fault location and cause of the fault by smelling through the nose. When inspecting the abnormal operation of the compressor, if you smell a burnt smell from the starter, it means that the starter is abnormal; if you smell a burnt smell from the power cord, it means that the power cord is abnormal; if you cut the Juyi pipe of the compressor factory If you smell a peculiar smell from the refrigeration lubricating oil, it means that the refrigeration lubricating oil has deteriorated.
(3) Voltage measurement method
The voltage measurement method is a method to determine the fault location and cause of the fault by detecting whether the voltage at the suspected point is normal.
When troubleshooting a refrigerator that does not work, you can measure the voltage at the mains socket to determine whether the fault is caused by an abnormality in the mains power supply line or socket, or by an abnormality in the refrigerator circuit. If the socket has an AC voltage of about 220V, it means that the power supply is normal and the fault occurs in the refrigerator circuit, as shown in Figure 25. After confirming that the refrigerator is abnormal, check whether the power supply of the compressor is normal. If it is normal, it means that the compressor is abnormal; if the voltage is abnormal, it means that the power supply line, thermostat, and starter are abnormal.
(4) Resistance measurement method
Resistance measurement method is one of the most important maintenance methods for electrical systems. This method is to determine the fault location and cause of the fault by testing whether the resistance of the suspected power line and device is normal. Of course, use the 200Ω scale (digital multimeter) or Rx1 scale (pointer multimeter) to basically confirm whether they are normal by measuring the resistance between the power supply terminals of the compressor, motor, and thermostat. For example, to test whether the electrical system of the refrigerator is normal, the resistance measurement method is more useful. See Figure 26. When the knob of the thermostat is not in the 0 position, measure the resistance between the neutral and live wires of the power plug. , it should be the resistance of the compressor winding. If the resistance is infinite, it means that the thermostat or circuit is open; similarly, if the resistance is still the resistance of the compressor winding after adjusting the thermostat to 0, then Indicates that the contacts of the thermostat are short-circuited. In addition, use the 200MΩ block of a multimeter to measure the resistance between the ground pin of the power plug and the other pin. The resistance should be infinite. If the resistance is small, it means the thermostat, overload protector, or compressor is leaking.
Note: The resistance must be measured with the power off to avoid damaging the multimeter.
Methods and techniques:
When detecting whether the power cord, hammer starter, overload protector and other devices are open circuit, you can use the "on/off" setting of the multimeter (some multimeters should The function is attached to the "PN voltage drop" gear) for measurement. If the multimeter makes a beeping sound, it means it is normal; if there is no beeping sound, it means the circuit is open; if the beeping sound comes and goes, it means the contact is poor.
(5) Temperature measurement method
The temperature measurement method is a method to determine the fault location and cause of the fault by measuring whether the temperature of key components of the refrigerator is normal: the visual inspection method introduced earlier The method of touching the inside of the refrigerator includes temperature measurement: In addition, an electronic thermometer is placed in the refrigerator box. By detecting the temperature in the box, it can be accurately judged whether the cooling effect of the refrigerator is normal.
(6) Pressure leak detection method
The pressure leak detection method is to forcibly fill the refrigeration system with nitrogen or air, so that the pressure in the system reaches 1.5MPa. Apply detergent (or soapy water) and observe whether there are bubbles to find leaks in the refrigeration system, as shown in Figure 28. The refrigeration system can be pressurized by filling it with nitrogen or using a modified compressor. Although the nitrogen pressure effect is good, the equipment is expensive, and general maintenance personnel usually do not use this method. Although the pressure using a modified compressor is slow, it has the advantage of being economical and practical.