LG Air Conditioner Error Code 28

Error code 28 on an LG air conditioner indicates a DC link high voltage fault in the inverter circuit. On single-phase models, the DC link voltage has exceeded 140Vdc, and on three-phase models it has exceeded 250Vdc. The system shuts down automatically to protect the inverter components from damage. This fault requires inspection of the incoming power supply, wiring connections, DC link capacitors, and the TRANS1 transformer.

The error code itself means the unit has already shut down to protect itself, so the immediate risk of further component damage is contained once the system has stopped. However, the underlying cause, which may involve overvoltage on internal capacitors or the power supply, represents a real electrical hazard if the unit panels are opened without proper precautions. Always disconnect power and allow DC link capacitors to discharge fully before working inside the inverter section.

Repair costs vary depending on which component is at fault. If the issue is simply a loose wiring connection, the cost may be limited to a service call fee, typically in the range of $75 to $150. If DC link capacitors need replacement, parts and labor can range from $150 to $400 depending on the unit. A failed inverter control board is the most expensive scenario, with parts and labor potentially ranging from $300 to $700 or more depending on the model.

Some basic checks, like inspecting the U, V, and W wiring connections for looseness or corrosion, can be done by a knowledgeable technician. However, measuring DC link capacitor voltage and diagnosing TRANS1 involve exposure to potentially lethal DC and AC voltages inside the inverter section. Most homeowners should not attempt this repair, and it is strongly recommended to have a qualified HVAC or appliance technician perform the diagnosis and any component replacement.

A power reset may temporarily clear the fault and allow the unit to restart, but if the underlying cause, such as a degraded capacitor, high line voltage, or a wiring fault, is still present, the error will return. Repeatedly resetting the unit without addressing the root cause can result in further damage to the inverter board or compressor. The fault should be properly diagnosed and repaired before returning the unit to normal operation.