Ask, watch, listen, touch, test, etc. to know the refrigerator failure

Ask, watch, listen, touch, test, etc. to know the refrigerator failure

Refrigerator failure inspection methods can generally be divided into asking, watching, listening, touching and testing. Through inspection, comprehensive analysis and judgment, gradually narrow the scope of the fault and find the point of failure.

　　 One, ask

First ask about the usage, failure phenomenon and service life of the refrigerator, especially the old machine. To understand the failure history of the machine and the usage after previous repairs, pay more attention to the ice block and dirty block of the machine that has repaired the refrigeration system. , Air mixing, whether the refrigerant oil has deteriorated, etc.

　　Second, look

　　A. First look at the frosting of the evaporator. When the compressor is running, if there is no frost on the surface of the evaporator, the frost is not full or the frost is not solid, it means that the refrigeration system is not working properly.

b. The freezer compartment of the refrigerator is icy, indicating that the temperature difference of the thermostat is too large, and the downtime is too long. The evaporator of the refrigerator compartment of the direct cooling double-door refrigerator is always full of frost without frosting and defrosting alternately. , Indicating that the thermostat is malfunctioning.

　　C. Check all the welds of the pipes in the refrigeration system and the surface of the evaporator to see if there are any traces of leakage. There will be oil stains in all the leaks.

　　D. Check whether the return pipe of the compressor is frosted. If it is frosted, it means that the amount of refrigerant is too much. For indirect cooling refrigerators, if the return pipe of the compressor is frosted, consider whether it is caused by the fan not turning. In this case, you can open the box door and press the door frame button to see if the fan rotates.

　　E, check if there is a gap in the door. If there is a gap in the door, the refrigerator has a long heat preservation performance, resulting in a long compressor startup time, a short shutdown time, and more frost in the refrigerator.

　　ш、Listen

　　A. Turn on the refrigerator. If you hear a “click" sound from the starter, the compressor will start within 0.2 seconds to 0.5 seconds, and then the compressor will emit a slight and rhythmic sound, indicating that the compressor starts normally.

For example, the compressor makes a dull "hum" sound, and then continuously hears the "click" starter contact disconnection and pull-in sound, sometimes with compressor vibration, and finally the thermal protector can be heard With a bang, the compressor was turned off. The following reasons can be considered for this failure:

　　A. The power supply voltage is low, the compressor cylinder is stuck, and the cylinder shaft is held;

　　B. Electric motor sweeps the hall;

　　C. Short circuit of motor winding;

　　D. The motor start winding is open;

　　E. Blockage of gas system pipeline;

　　F. Start relay failure, etc. Use the elimination method to determine the cause of the failure.

　　 B. When the compressor is running, there is a clear jet sound in the casing, indicating that the compressor exhaust buffer pipe is broken and leaking. If the compressor casing cracks, it means that the compressor high and low pressure valves are broken and leaking. When the compressor just shuts down, you hear a clear sound of outgassing in the casing, indicating that the high and low pressure paper gasket of the compressor valve plate is broken down, the exhaust shock absorber tube is leaking, the valve plate is worn or the valve plate and valve port are accumulated. carbon. When the compressor is running, if the casing makes a "dangdang" impact sound, it indicates that the support spring in the compressor is broken or deformed by fatigue.

　　C, the high-pressure liquid refrigerant enters the evaporator through the capillary tube, evaporates quickly, and at the same time emits a "hissing" airflow sound, and often accompanied by the sound of water, which is a normal phenomenon. If you hear a "chick" sound in the evaporator, or intermittent suffocation sound, the fault is usually dirty, oil, or ice. The intermittent jet sound with long periodicity is generally an ice block. If there is only air flow in the evaporator and no frost, it means that the refrigerant in the system has basically leaked.

　　D. Refrigerators sometimes make intermittent noises, which are often caused by resonance caused by the unstable feet of the refrigerator, the collision of refrigeration system pipes, and the loosening of screws on the compressor and cabinet base.

　　Four, touch

　　 When the refrigerator is operating normally, the temperature of each part of the refrigeration system can be touched to make a rough judgment of the refrigeration system condition. (The temperature of each part of the refrigeration system is also affected by the ambient temperature. When the ambient temperature rises, the temperature of the condenser, filter, return pipe and compressor will increase significantly. On the contrary, the temperature of the above-mentioned parts will decrease significantly.)

　　A. When the compressor is running, touch the upper part of the condenser and it should be very hot (above 55°C). If it is not hot, it may be caused by a leak or blockage in the refrigeration system or the compressor has no discharge pressure.

　　B. When it is normal, you should feel hot when touching the filter dryer (about 55°C). If the refrigeration system is too dirty, the temperature of the filter drier will rise. For the refrigerator that has just been repaired, if the temperature of the filter drier is too high, the capillary flow resistance is generally too large and the refrigerant charge is too large.

　　C. When the compressor is working normally, touch the compressor return pipe, there should be no heat (close to the ambient temperature). If the temperature is high, it means that the system is lack of refrigerant, the pipeline is slightly blocked or the system is mixed with air. If you feel cold or there is dew or even frost, it means that the refrigerant charge is too much.

　　D. The temperature of the compressor casing is generally below 70°C. Even in summer, when the refrigerator is turned on for the first time, the compressor has been working continuously for a long time, and the cabinet temperature does not exceed 85°C.

　　E. If the frost on the evaporator falls off by touching it by hand (called virtual frost), and the compressor return pipe is full of frost, it means that the refrigerant charged is too much or the newly replaced capillary tube is too thick or too short.

　　F. Touch the surface of the evaporator with your hands. If you find that the evaporator is not full of frost, it means that the system has insufficient refrigerant or the capillary is half blocked.

　　 Five, test

　　Inspect the refrigerator by measuring the temperature, pressure, startup and shutdown ratio, operating current, and the insulation resistance and DC resistance of the compressor.

　　A, temperature measurement:

　　B, pressure measurement:

　　 Check the pressure-enthalpy diagram, suction (0.04Mpa), exhaust (1.39Mpa) pressure (refer to R12 for working conditions).

　　A. The suction pressure is too high, usually caused by: too much refrigerant charge, too short a new capillary tube, compressor performance.

　　B. When the suction pressure is negative, it is usually caused by: insufficient refrigerant, blockage in the system, and the new capillary tube is too thin and too long.

　　C, measure the ratio of the refrigerator's start-up and shutdown:

　　The ratio of starting and stopping the refrigerator is directly related to its refrigeration system, heat preservation performance, thermostat performance, adjustment position, ambient temperature, circuit system, the amount of food in the refrigerator, and the number of times the door is opened.

　　D, measuring working current:

　　A. If the working current is greater than the rated current, it means that the refrigerant charge is too much, the refrigeration system is slightly blocked, and the compressor is partially short-circuited.

　　B. If the working current is less than the rated current, it means that the refrigeration system is leaking or the system is completely blocked.

　　E. Measure insulation resistance and DC resistance: (For motor windings that are not severely short-circuited or have poor inter-turn insulation, it is difficult to distinguish motor faults with resistance measurement methods, so they can only be judged by measuring the working current)