LG Air Conditioner Error Code CH28

CH28 indicates that the inverter PCB has detected a DC link voltage above 420V, which causes the compressor to shut down for protection. The error is only displayed after this overvoltage condition occurs five separate times, meaning the problem is persistent rather than a one-time spike. The fault points to either a high incoming AC supply voltage or a problem with the inverter control board itself.

The CH28 fault is a protective shutdown designed to prevent damage to the power electronics inside the unit. The system shuts off the compressor automatically when the DC link exceeds 420V, reducing the risk of component failure or electrical damage. However, repeated overvoltage events on your electrical supply can indicate a broader wiring or utility issue that should be investigated for household safety.

Repair costs depend on the root cause. If the issue is simply high supply voltage corrected by an electrician, costs could range from $100 to $300 for diagnosis and any wiring adjustments. If the inverter PCB needs replacement, parts and labor combined typically range from $300 to $700 or more depending on the model and local labor rates.

A homeowner can start by checking whether the incoming electrical supply voltage is within the normal range for their unit, which does not require opening the air conditioner. However, diagnosing or replacing the inverter PCB involves working with high voltages and should be performed by a qualified technician. If the supply voltage is normal and the fault persists, professional service is strongly recommended.

Resetting the air conditioner may temporarily clear the displayed fault code, but CH28 requires five separate overvoltage occurrences before it is reported, meaning the underlying condition has already happened multiple times. If the cause is not corrected, the fault will return. A reset is only appropriate after the root cause, such as high supply voltage or a faulty PCB, has been identified and resolved.