Samsung Air Conditioner Error Code E255

E255 indicates an open circuit or short circuit fault with the MCU temperature sensor on the main PCB. This sensor monitors the temperature of the microcontroller unit on the control board. When the PCB cannot read a valid resistance signal from the sensor, it triggers this error and may suspend normal operation to protect the electronics.

It is not advisable to continue operating the unit while the E255 error is active. The MCU temperature sensor exists to protect the control board from overheating, and without a valid reading, the system has no way to detect a developing overheat condition. Continued operation could risk damage to the PCB or other electrical components.

A power reset may temporarily clear the E255 error code, but if the underlying sensor fault still exists, the error will return once the unit attempts to read the sensor again. A reset alone does not repair a disconnected connector, damaged wiring, or a failed sensor. Proper diagnosis and correction of the root cause are required for a lasting resolution.

Some causes of E255 are DIY-friendly, such as reseating a loose connector or cleaning corroded terminals. You will need a multimeter to measure resistance across the sensor terminals to determine whether the sensor itself has failed. If the sensor or wiring harness needs replacement, comfort with basic electrical work and component sourcing is required. If you are unsure about working around control board components, a qualified technician is recommended.

If only the sensor connector needs reseating or cleaning, there may be no parts cost, though a service call will carry a labor fee typically in the range of $75 to $150. If the MCU temperature sensor itself requires replacement, parts and labor combined generally range from $100 to $300 depending on the specific unit model and local labor rates. Control board replacement, if the board is also damaged, can increase costs significantly.