⚠️ SAFETY WARNING / ELECTRICAL AND FLAMMABILITY RISK. This appliance operates at mains voltage (230V) and uses flammable refrigerant gas (R600a). Before any visual inspection, always disconnect the power plug from the electrical outlet. Interventions on the sealed gas circuit and live electrical parts must be carried out exclusively by a qualified F-GAS technician to avoid risks of electrocution or fire. This diagnosis is provided EXCLUSIVELY for educational and informational purposes.
CAUSE A: Internal mechanical failure of the linear compressor
- Probability: 85% (Very High)
- Key symptoms: The compressor vibrates noticeably in jerks, produces an intermittent metallic hum, overheats quickly, and generates no temperature difference between the discharge and return pipes.
- Technical analysis: In LG linear compressors, the piston is coupled to a magnet that oscillates linearly thanks to resonance springs. It often happens that, after years of operation, these internal springs weaken or break. The piston loses its perfect axis, hits the cylinder walls, and jams. The lack of compression cancels the R600a refrigerant gas cycle, completely preventing cooling.
- False positives: A similar vibration can be caused by loose leveling feet or external copper pipes vibrating against the body, but in that case, the refrigerator continues to cool normally.
COMPARATIVE TABLE OF FAULT CAUSES
| Cause of the Fault | Probability | Main Symptom | Component Involved | Type of Intervention |
| :--- | :--- | :--- | :--- | :--- |
| Mechanical Failure | 85% | Jerky vibration, metallic hum, no cooling | Inverter Linear Compressor | Replacement (F-GAS Technician) |
| Inverter Board Failure | 10% | Absence of pulses, no startup attempt | Power electronic board | Board replacement (Partial DIY) |
| Circuit Obstruction | 5% | Short startup, overheating, clixon tripping | Capillary tube / Filter drier | Circuit flushing / Filter replacement |
CAUSE B: Failure of the driving inverter electronic board
- Probability: 10% (Low)
- Key symptoms: Total absence of vibration or weak and irregular electrical pulses sent to the compressor, without any real startup attempt being initiated.
- Technical analysis: The inverter board controls the frequency and voltage of the compressor solenoid. If the filter capacitors or the IGBT power modules of the board degrade, the driving signal is distorted or insufficient to overcome the initial inertia of the magnet.
- False positives: The board could go into safety lockout (cutting the voltage) not because it is faulty, but as a protective reaction to an overload caused by the already seized compressor (Cause A).
CAUSE C: Total obstruction of the refrigerant circuit
- Probability: 5% (Very Low)
- Key symptoms: The compressor starts, vibrates normally for a few minutes, but overheats until the thermal protector (clixon) trips, without cooling.
- Technical analysis: If the Teflon seal of the piston deteriorates, it releases micro-fragments that clog the filter drier or the capillary tube. The compressor attempts to push the gas against a total blockage, increasing the internal pressure until thermal shutdown.
WHICH IS YOUR CASE?
🛠️ Quick checks for diagnosis
- The touch test: Carefully touch the discharge pipe (the narrower copper one coming out of the compressor). If the motor vibrates but the pipe remains at room temperature after 5 minutes, compression is absent (confirms Cause A).
- The acoustic test: Listen to the back of the fridge. If you hear a metallic "clack" every 3-5 minutes followed by total silence, the thermal protection is disconnecting the compressor due to overcurrent.
- Ohmic measurement: Unplug the power, remove the compressor electrical cover, and measure the resistance between the pins. An open value (infinite) or zero indicates a burned winding.
For LG FLB075LANA models, the correct nominal resistance between the pins must measure exactly between 7.2 and 9.2 Ohms: any significantly different or unstable value confirms irreversible damage to the internal stator.
🔧 Tools and Spare Parts needed for the technician
For an instrumental evaluation and eventual restoration, the following are required:
📋 Report for your trusted technician
"The LG refrigerator exhibits a lack of cooling associated with jerky vibrations of the linear compressor. The stator windings show compliant resistance values, but the discharge pipe remains cold during startup attempts. Internal resonance spring failure or piston seizure is suspected. Testing of the inverter board output voltages is requested to rule out driving issues before proceeding with eventual compressor replacement and weighed recharge of R600a."
OPERATIONAL DECISION: If the compressor vibrates in jerks but the inverter board signal is correct, the repair requires an F-GAS technician and is economically disadvantageous out of warranty (estimated cost €350-500): replacing the refrigerator is recommended.
Caricamento interfaccia di diagnosi...
