Samsung Air Conditioner Error Code 123

Error code 123 on a Samsung air conditioner indicates a problem with the indoor unit heat exchanger outlet temperature sensor. The control board has detected either an open circuit or a short circuit from this sensor, which can be caused by a disconnected connector, a broken wire, or a failed sensor component. The unit shuts down to prevent operating without valid temperature data.

A power reset may temporarily clear the error code from the display, but if the underlying wiring or sensor fault still exists, the code will return as soon as the unit attempts to operate and reads the faulty sensor signal. The physical problem must be corrected before the unit will run reliably without displaying error 123 again.

Repair costs vary depending on the cause. If the fix involves only reseating a connector, there may be no parts cost at all, with a service call fee typically in the range of $75 to $150. Replacing the out-temp sensor itself is generally a low-cost part, with total repair estimates commonly falling between $100 and $250 including labor. Wiring harness replacement or control board involvement would raise costs further.

Some causes are approachable for a knowledgeable DIYer, particularly reseating a loose connector or visually inspecting the sensor wiring for obvious damage. However, testing the sensor with a multimeter and replacing the sensor or wiring harness requires comfort working inside the indoor unit and handling electrical components. If you are not confident with these steps, a certified HVAC technician should perform the diagnosis.

It is not advisable to attempt to bypass or ignore this fault and continue operating the unit. The indoor heat exchanger outlet sensor provides temperature feedback that the control board uses to regulate the refrigeration cycle. Running without this data could result in evaporator icing, compressor stress, or other secondary damage. The fault should be resolved before resuming normal operation.