LG Heat Pump Error Code G9

The G9 code indicates an OPEN or SHORT circuit error in the EVAP OUT sensor inside the indoor unit. This thermistor monitors refrigerant temperature at the evaporator outlet. When the PCB detects a resistance reading outside the normal range, it shuts the system down and displays G9. In multi-zone systems, the number accompanying the code identifies which indoor unit is affected.

The system is designed to stop normal operation when the G9 fault is detected, which means it will not heat or cool effectively with this error active. Attempting to force the unit to run without resolving the sensor fault could allow the system to operate outside safe parameters. It is best to leave the unit off until the fault is diagnosed and corrected.

A power reset may temporarily clear the G9 code and allow the unit to restart, but if the underlying sensor or wiring fault is still present, the error will return quickly. Resetting the unit without repairing the cause is not a reliable fix. A proper diagnosis of the EVAP OUT sensor circuit is required to resolve the fault permanently.

A homeowner with basic electrical knowledge can safely check whether the sensor connector has come loose at the indoor PCB and reseat it. However, testing thermistor resistance, inspecting wiring harnesses, and replacing sensors or circuit boards requires a multimeter and familiarity with electronic components. If reseating the connector does not clear the fault, a qualified technician should perform the remaining diagnostic steps.

Repair costs vary depending on the root cause. If only the sensor connector needs reseating, a service call fee in the range of $75 to $150 may be the only cost. Replacing a failed EVAP OUT thermistor typically adds parts and labor bringing the total to roughly $150 to $350. If the indoor PCB requires replacement, costs can range from $300 to $600 or more depending on the model and labor rates in your area.