LG Air Conditioner Error Code 174

Error code 174 indicates a failure of the Sub1 constant speed compressor 1 to operate. The code covers three specific failure modes: mechanical compressor locking, check valve leakage or incorrect installation, and dielectric breakdown of the compressor motor windings. A technician will need to test each of these conditions to determine the actual cause.

No, you should not continue operating the unit with this fault active. A dielectric breakdown in the compressor creates a risk of electrical short circuit, and a seized or failing compressor can cause additional damage to the refrigerant system. Shut the system off and contact a technician for diagnosis.

Repair costs vary significantly depending on the root cause. A check valve replacement or wiring repair is relatively inexpensive, typically in the range of $150 to $400 including labor. A compressor replacement is considerably more expensive, often ranging from $800 to $2,000 or more depending on the unit size and refrigerant type. A technician diagnostic visit is usually required before any cost estimate can be confirmed.

Most repairs related to this code require professional tools and certifications. Testing insulation resistance requires a megohmmeter, and any work involving refrigerant or high-voltage compressor components should be performed by a licensed HVAC technician. Homeowners can check for obvious wiring issues but should not attempt to bypass or operate the compressor manually.

A power reset may temporarily clear the fault display, but the code will return as soon as the system attempts to start the compressor again if the underlying problem has not been repaired. The fault is tied to a real hardware condition, not a communication glitch, so resetting without repairing will not resolve it.