Error code after servicing cleared with PCB reset, not board replacement

What we found

An error code that appears right after servicing strongly suggests a power-related fault state, not a component failure. We checked the error log and tested the board's response before assuming it needed replacing.

• Error code corresponded to a communication or power fault — consistent with an abrupt power interruption
• Error log showed the fault was timestamped at the same period as the servicing visit
• PCB responded to the manufacturer's reset sequence — the board was not dead
• After clearing the error state and powering the unit back on correctly, it resumed normal operation

During the previous servicing visit, power was cut at the isolator while the indoor unit was still running. The PCB did not complete its shutdown cycle and locked into a protective error state. The board itself was functioning. It was waiting for the error to be acknowledged and cleared.

What we did

The reset sequence cleared the error and the unit returned to normal operation. No board replacement was needed. Power should always be shut down through the remote or wall controller before switching off the isolator during servicing.

The error code was cleared and the unit resumed cooling normally. The original PCB remains in the unit. No parts were replaced and the warranty was not affected.

What we learned

Error code after servicing — dead board vs locked board.

• When power is cut to an aircon mid-cycle, such as during servicing, the PCB can lock into a fault state. The board stores the error and refuses to restart. It needs the correct reset procedure to clear.
• A locked PCB responds to a reset sequence. A dead PCB does not respond at all. Checking this distinction is quick and can save the cost of a board replacement.
• On newer units still under warranty, an unnecessary board replacement can complicate the warranty claim. This applies when the original board was not actually faulty.