LG Air Conditioner Error Code E277

E277 indicates an error on the top temperature sensor of compressor 2, detected as either a short circuit or an open circuit condition. This sensor is a thermistor that monitors compressor top temperature to prevent overheating. When the PCB receives a signal outside its valid resistance range, it triggers E277 and restricts or shuts down that compressor circuit. The first thing to check is whether the sensor connector has come loose from the control board.

A power reset may temporarily clear the fault code, but E277 will return if the underlying sensor issue is not corrected. If the connector is simply loose, reseating it and resetting the unit may resolve the problem permanently. If the sensor or wiring has physically failed, the fault will reappear once the system restarts and the PCB reads the faulty signal again.

Repair costs vary depending on the root cause. If only the connector needs reseating, a service call fee in the range of $75 to $150 may be the only cost. Replacing the compressor top thermistor sensor typically adds parts costs in the range of $20 to $80 for the sensor itself, plus labor. If wiring harness damage requires more extensive repair, total costs could range from $150 to $400 or more depending on the system configuration and technician rates.

Some causes of E277 are accessible to a knowledgeable DIYer, such as reseating a loose connector or inspecting the wiring harness for obvious damage. However, working inside a multi-zone or commercial AC system involves high-voltage components and refrigerant circuits, so any deeper diagnostics or repairs should be performed by a qualified HVAC technician. Replacing the compressor top sensor itself is a straightforward component swap once the fault is correctly isolated.

It is not recommended to continue operating the system with E277 active. The top compressor sensor is a protective device that prevents the compressor from running in an overtemperature condition. Without reliable sensor feedback, the compressor could operate outside safe temperature limits, potentially causing permanent compressor damage. The system may already be limiting or halting compressor 2 operation as a protective measure.