LG Air Conditioner Error Code 111

Error code 111 on an LG air conditioner indicates a communication error between the main outdoor unit and the sub1 outdoor unit. The sub1 PCB is not receiving the signal from the main outdoor unit. This fault appears in multi-outdoor-unit LG systems and prevents the units from coordinating operation. The first step is to check the DIP switch settings and the communication cable connections between the two outdoor units.

Error 111 is a communication fault rather than a safety-critical failure, so it does not pose an immediate hazard. However, it does prevent the sub1 outdoor unit from operating properly, which can reduce system capacity and efficiency. The system should be serviced promptly to restore full operation and prevent additional strain on the main outdoor unit.

A power reset may temporarily clear the error display, but error 111 will return if the underlying communication fault is not resolved. The sub1 PCB will continue to fail to receive the main unit signal until the wiring, DIP switch settings, or faulty PCB is corrected. A reset is useful for confirming whether the fault is intermittent, but it is not a permanent fix.

Some causes of error 111 are accessible to a knowledgeable DIYer, such as visually inspecting communication cable connections and verifying that terminals are firmly seated. However, checking DIP switch configurations requires access to the outdoor unit PCBs and knowledge of the specific wiring diagram for your system. Diagnosing or replacing a failed PCB should be handled by a qualified technician, as it involves working with live electrical components.

Repair costs vary depending on the root cause. If the fix involves reseating a cable connection or correcting DIP switch settings, labor costs may range from around $75 to $200 depending on your area. If a communication cable needs to be replaced, expect to add $20 to $100 in parts. PCB replacement is significantly more expensive, with parts and labor potentially ranging from $300 to $800 or more depending on the specific board and system model.