LG Air Conditioner Error Code CH55

CH55 on an LG air conditioner indicates a communication error where the outdoor unit is not successfully receiving data from the central controller. This fault is specific to the signal pathway from the controller to the outdoor unit. The system will typically stop normal operation until the communication issue is resolved. It is most commonly caused by wiring faults, a damaged communication cable, or a failed control board.

A power reset may temporarily clear the CH55 code, but if the underlying wiring or component fault is still present, the error will return shortly after the system attempts to resume communication. A reset alone is not a fix. The root cause must be identified and corrected before the system will operate reliably without re-triggering the fault.

Repair costs vary depending on the cause. If the fix is a loose wire or a replacement communication cable, costs are typically in the range of $75 to $250 including labor. If the outdoor unit control board or central controller needs replacement, costs can range from $300 to $900 or more depending on the specific model and part availability. A diagnostic service call is usually needed first to pinpoint the exact cause before parts are ordered.

Homeowners can check for obviously loose or disconnected wiring at accessible terminal blocks, but most diagnostic steps require a multimeter and knowledge of low-voltage communication circuits. If simple connection checks do not resolve the error, a qualified HVAC technician should inspect the communication wiring, control boards, and central controller settings. Working inside the outdoor unit also involves exposure to high-voltage components, so professional service is recommended for anything beyond a visual inspection.

When CH55 is active, the outdoor unit is not receiving proper commands from the central controller, so the system is likely already in a fault state and not operating normally. Attempting to force operation without resolving the communication fault could lead to improper system behavior. It is best to leave the unit off and arrange for diagnostic service rather than attempting to run it through the error.