LG Air Conditioner Error Code 177

Error code 177 indicates a failure in the Sub2 constant speed compressor 2 operation on your LG air conditioner. The fault can stem from compressor mechanical locking, check valve leakage, or dielectric breakdown of the compressor motor windings. The control system detected that this secondary compressor is not functioning within normal operating parameters. A technician will need to perform specific electrical and mechanical checks to isolate the root cause.

It is not advisable to continue running the system with code 177 active. A compressor with dielectric breakdown poses a risk of electrical faults, and a locked compressor can cause additional damage to the system if run attempts are repeated. Shut the unit down and contact a qualified technician for inspection.

A power reset may temporarily clear the error code from the display, but it will return if the underlying fault has not been corrected. Compressor locking, check valve failure, and dielectric breakdown are physical or electrical conditions that do not resolve on their own. The system should be properly diagnosed and repaired before returning it to service.

This error requires diagnostic steps that involve working with high-voltage compressor circuits and measuring insulation resistance with a megohmmeter, which are tasks suited for a trained HVAC technician. A homeowner should not attempt to press magnetic switches or probe compressor terminals without proper training and safety equipment. If the compressor has locked up or suffered dielectric breakdown, professional repair or replacement is necessary.

Repair costs depend heavily on the root cause identified during diagnosis. Check valve replacement or wiring repairs are relatively inexpensive, typically ranging from $100 to $400 including labor. Compressor replacement on a multi-compressor commercial or mini-split system is significantly more costly, often ranging from $800 to $2,500 or more depending on unit size, compressor model, and labor rates in your area.