LG Air Conditioner Error Code E129

E129 means the EVA OUT temperature sensor on the indoor unit has been detected as detached from the evaporator outlet pipe. This thermistor monitors the temperature of refrigerant leaving the evaporator coil, and when it loses contact with the pipe, the control board receives an inaccurate or out-of-range reading and triggers the fault. The unit will typically stop operating until the issue is resolved.

It is not recommended to continue running the unit while E129 is active. Without an accurate evaporator outlet temperature reading, the system cannot properly regulate its cooling cycle, which can lead to evaporator freeze-up, compressor strain, or inefficient operation. The unit may shut itself down automatically as a protective measure.

Resetting the unit by powering it off and back on may temporarily clear the code, but the error will return if the underlying issue with the sensor has not been resolved. A reset is useful only after the sensor has been properly reattached and confirmed to be reading correctly. Relying on repeated resets without fixing the root cause can mask the problem and lead to further system damage.

If the sensor has simply slipped off the pipe, a knowledgeable DIYer can reattach it by firmly pressing it back against the pipe and securing it with the retaining clip or foam tape. However, if the thermistor needs resistance testing or the sensor wire shows damage, a qualified technician with a multimeter and access to replacement parts is the better choice. Opening the indoor unit also requires careful handling to avoid damaging other components.

If the sensor only needs to be repositioned and clipped back in place, the cost may be limited to a service call fee, typically in the range of $75 to $150. If the thermistor needs to be replaced, parts and labor combined generally fall in the $100 to $250 range depending on the model and your location. Wiring or control board repairs would push costs higher.