LG Air Conditioner Error Code 136

Error code 136 means the system has detected an open or short circuit condition in the temperature sensor on the rear-side heat exchanger (B) of the sub2 outdoor unit. This sensor is a thermistor that monitors heat exchanger temperature, and the control board has determined its signal is outside the expected range. The system flags this fault to prevent operating with unreliable temperature data. Diagnosis follows the CH45 procedure, which involves testing the sensor resistance and inspecting the associated wiring.

Continuing to operate the system with this fault is not advisable. The affected outdoor unit may already be restricted or shut down by the control system as a protective measure. Running the system without accurate heat exchanger temperature data risks improper refrigerant management and potential compressor damage. The fault should be diagnosed and resolved before returning the unit to normal operation.

A power reset may temporarily clear the error code, but if the underlying fault with the sensor or wiring still exists, the code will return once the system restarts and re-evaluates the sensor signal. Resetting without diagnosing and repairing the root cause does not resolve the problem. The CH45 diagnostic procedure should be completed to identify and fix the actual fault before relying on normal operation.

Some basic checks, such as inspecting the wiring harness and connector for visible damage or corrosion, can be done by a knowledgeable DIYer. However, properly testing the thermistor resistance, tracing the wiring through an outdoor unit, and replacing components in a multi-unit system requires technical familiarity with HVAC systems and a multimeter. If the sensor or control board needs replacement, a qualified HVAC technician is recommended.

Repair costs depend on the root cause. A thermistor sensor replacement is typically a relatively low-cost part, with total repair costs including labor often ranging from around $100 to $300. If the outdoor unit control board has failed, parts and labor costs can range from $300 to $700 or more depending on the specific system. Wiring repairs fall somewhere in between depending on the extent of the damage.