Common Fault Analysis and Repair of Refrigerator Compressors
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### 1. Exhaust Failure
**Fault Symptoms**: When the refrigerator compressor is running, the condenser is not hot or only slightly warm, and there is a slight airflow sound inside the compressor, or the cooling effect is poor after prolonged operation of the compressor.
**Fault Causes**: After ruling out refrigerant leakage, blockage of the capillary tube, and the filter, the failure is likely due to a problem with the compressor's exhaust system. This mainly occurs due to the rupture of the high-pressure exhaust pipe or a blown gasket, causing the refrigerant to circulate inside the shell, producing airflow noise and resulting in poor or no cooling. Another cause may be insufficient compressor discharge, due to broken valve plates (caused by liquid hammering or poor material quality), valve plate carbon buildup (due to oil overheating and degradation), or excessive clearance between the piston and cylinder (due to wear and tear), all of which affect the cooling performance.
### 2. Noise Failure
**Fault Symptoms**: When the compressor is running, there is a "meowing" metallic knocking noise inside the shell.
**Fault Causes**: This type of failure is caused by severe deformation, dislocation, or breakage of the damping spring, which results in the spring losing its shock-absorbing function, causing the compressor body to strike against the inner wall of the casing, generating noise.
### 3. Shaft Seizure, Cylinder Sticking, or Shaft Wobbling Failure
**Fault Symptoms**: After powering on the refrigerator, the compressor does not run and emits a "buzzing" sound.
**Fault Causes**: When the power supply voltage, motor windings, and starter are normal, but the motor does not rotate, this fault is usually due to the compressor being "seized." This often occurs in the main shaft, piston, cylinder, and connecting rod areas. The main cause is blockage in the compressor oil circuit by contaminants, leading to poor lubrication and causing wear and seizure. Contaminants may stick to the piston (caused by varnish falling off enameled wire, which sticks to the cylinder and piston) or excessive clearance between the rotating shaft and sleeve, causing the rotor to be pulled to one side by electromagnetic force and become off-center when powered on, which is another reason for the motor failing to rotate.
### 4. Winding Failure
**Fault Symptoms**: The compressor does not turn on or runs abnormally when powered on.
**Fault Causes**: If the power supply, starter, and thermal protector are normal, use a multimeter to measure the compressor winding resistance and check if the operating winding and start winding resistances are normal. If the resistance tends toward infinity, it indicates an open circuit in the operating or start windings, or a detached lead socket. If the resistance is too low, there may be a short circuit between turns or phases. Use a megohmmeter to measure the insulation resistance between the terminals and the casing. If the resistance tends toward zero, it indicates a short circuit to ground in the operating or start windings. Compressors with these faults require disassembly for repairs.
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### Compressor Disassembly and Repair
When a compressor fault is diagnosed and it requires disassembly, the compressor should be removed from the refrigerator. Drain the oil and inspect its quantity (typically between 0–350 ml depending on the model) and check whether the oil has deteriorated. Darkened color, burnt smell, or lack of transparency indicate overheating or wear inside the compressor.
**1. Compressor Disassembly**:
For compressors with a circular socket, they can be mounted on a machine for disassembly. Flanged compressors can be cut open using gas welding at the welded seam. For oval socket compressors, they can be mounted on a vise and sawn open with a hacksaw. A grinding machine can also be used to open the casing for compressors of various shapes. After opening the compressor, unplug the internal wiring socket from the terminal, then loosen the high-pressure output pipe bolt and clamp, allowing the body to be removed from the shock-absorbing springs. Components should be cleaned with gasoline and oiled to prevent rusting.
**2. Valve Plate and Valve Repair and Assembly**:
Carbon buildup on high and low-pressure valves and valve plates should be scraped off with a wallpaper knife and ground flat (on a soft cloth or oiled glass). Deformed, worn, or broken valves should be replaced. When assembling the repaired low-pressure valve, pry the tip slightly to ensure a 0.2 mm gap between the tip and the valve plate hole to aid compressor startup. The high-pressure valve should have good sealing with the valve plate, which can be tested by dripping refrigerant oil into the high-pressure air hole of the valve plate. If no oil seeps out after five minutes, the seal is good.
**3. Repair and Assembly for Shaft Seizure or Cylinder Sticking**:
Soak the body in diesel fuel for a day, then manually turn the motor rotor to check for looseness between the shaft and frame. If loose, increase the rotation angle until the motor rotates freely. If the rotor doesn't loosen, disassemble the cylinder, sliding tube, and slider. Examine the piston and cylinder for wear or contamination and clean or repair as necessary.
**4. Oil Circuit Fault Repair**:
Disassemble the rotor from the shaft, clean the oil circuit, and reassemble. Ensure the balance weight on the rotor is in its original position.
**5. Other Mechanical Fault Repairs**:
For broken high-pressure output pipes, repair by welding or replacement. Replace any broken or deformed damping springs with identical ones.
**6. Compressor Winding Repair and Assembly**:
For winding damage, remove the original coil and rewind it using the appropriate enameled wire. Rewind as you would for a single-phase asynchronous motor. Ensure proper insulation and reassemble the compressor.
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### Example: Three-Door Refrigerator Not Working
**Analysis and Repair**:
After finding a defective compressor thermal protector, tests showed issues with the compressor windings. Further analysis revealed the compressor suffered damage due to prolonged operation without refrigerant, leading to excessive heat and failure. The system was recharged, leaks repaired, and the compressor replaced.
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### General Repair Methods
Regular maintenance is critical for prolonging the life of compressors. Routine inspections using methods such as visual inspection, listening, and touch can help identify potential problems early.