LG Air Conditioner Error Code 135

Error code 135 indicates that the temperature sensor monitoring the front-side heat exchanger (A) on the sub2 outdoor unit has an open or short circuit condition. The control board cannot get a valid reading from this thermistor and shuts down operation to protect the system. Diagnosis follows the CH45 procedure, which involves inspecting the sensor, wiring, and control board connections.

A power reset may temporarily clear the code and allow the unit to restart, but if the sensor or wiring fault is still present, the error will return quickly. The underlying cause must be repaired before the system will operate normally without retriggering the fault.

Repair costs vary depending on what component has failed. If only the sensor thermistor needs replacement, parts and labor costs typically range from around $75 to $200. If the wiring harness or the outdoor unit control board requires replacement, costs can range from $150 to $600 or more depending on the unit model and local labor rates.

A knowledgeable DIYer can check for obvious issues such as a loose or disconnected sensor connector at the outdoor unit control board. However, properly diagnosing an open or shorted thermistor requires a multimeter and knowledge of expected resistance values at given temperatures. Replacing components inside the outdoor unit is best handled by a certified HVAC technician.

Error code 135 typically causes the system to stop operating as a protective measure. Attempting to force operation without a functioning heat exchanger temperature sensor removes an important safeguard and could lead to coil damage or compressor issues. The fault should be repaired before resuming normal use.