LG HVAC Error Code 5

Error code 5 on an LG HVAC system means the indoor unit and outdoor unit control boards have lost communication with each other. The system shuts down when this link is interrupted because the units can no longer coordinate operation. Common causes include miswired connections, damaged communication wiring, or a blown fuse at one of the units. The signal type and voltage range differ between inverter and standard SEER models, so diagnosis must account for which system type is installed.

No, the system will not run while error code 5 is active because the communication failure prevents the indoor and outdoor units from coordinating safely. Attempting to force operation is not recommended. The system should remain off until the communication issue is identified and corrected.

Repair costs vary significantly depending on the cause. Replacing a blown fuse is inexpensive, typically in the range of a few dollars for parts plus a service call fee. Wiring repairs may cost somewhere between $100 and $300 depending on the extent of the damage and labor rates in your area. If an indoor or outdoor control board needs replacement, costs can range from $300 to $800 or more depending on the specific board and labor involved.

A knowledgeable DIYer can inspect the low-voltage communication wiring between the indoor and outdoor units and check that wire colors match at both sets of terminals. Checking and replacing fuses at both units is also within reach for someone comfortable working with low-voltage wiring. However, measuring the floating DC communication signal requires a manually set DC voltmeter and some familiarity with reading these signals. If wiring and fuses are not the issue, diagnosing a failed control board typically requires a qualified technician.

A power reset may temporarily clear the error display, but if the underlying wiring or component issue remains, error code 5 will return as soon as the system attempts to restart and re-establish communication. A reset alone is not a fix and should be followed by a proper diagnostic inspection of the wiring and fuses.