LG Heat Pump Error Code E155

E155 is a mixed operation error, meaning the system has detected that heating and cooling modes are being commanded simultaneously across the heat pump circuit. LG heat pump systems cannot run both modes at the same time through the same refrigerant circuit. The system shuts down as a protective measure until the conflict is resolved. This fault is most common in multi-zone systems with multiple indoor units.

No. The E155 error is a protective lockout, and the system will generally not allow normal operation while the fault is active. Attempting to force the system to run in a mixed operation condition could cause compressor damage, refrigerant circuit problems, and potentially costly repairs. Address the fault before resuming use.

Repair costs vary depending on the cause. If the fix involves simply correcting thermostat or controller settings, there may be no parts cost and only a service call fee, typically in the range of $75 to $150. If a faulty indoor or outdoor unit PCB is involved, parts and labor combined can range from $200 to $600 or more depending on the specific board and labor rates in your area.

In many cases, yes. Start by checking all indoor unit remote controllers and thermostats to confirm they are all set to the same mode, either all heating or all cooling. If the settings appear correct and the error persists after a reset, the fault may involve a wiring issue or a defective control board, which typically requires a qualified technician to diagnose and repair.

A power reset may temporarily clear the error, but it will return if the underlying cause is not corrected. If conflicting mode settings are the root cause, correcting all indoor unit settings before or after the reset will prevent the fault from reappearing. If a faulty PCB or wiring issue is responsible, the error will come back after reset until that component is repaired or replaced.