Error code after power surge cleared with PCB reset, not replacement

What we found

Post-surge error codes need the error history read first. A board in protection mode and a board with actual component damage show different diagnostic patterns.

• Error code matched the manufacturer's protection lockout code, not a component failure code
• Error history showed a single event coinciding with the reported surge — no prior fault codes
• No visible burn marks, swollen capacitors, or damaged components on the PCB
• Board passed a visual inspection and showed normal standby voltage at the test points

The site-wide power surge triggered the outdoor PCB's built-in voltage protection. The board entered lockout mode to prevent damage. The flag remained set, stopping the unit from restarting. The board itself was not damaged.

What we did

The PCB is not damaged. It is in lockout after the surge. The correct reset clears the flag and restores normal running. No board replacement is needed. We perform the reset and confirm the unit runs a full cycle without tripping again.

After the proper reset, the error code cleared and the unit restarted. The system ran through sustained use with no further error codes. No PCB replacement was needed.

What we learned

Why post-surge error codes are often protection lockouts, not damage.

• Many aircon PCBs enter a lockout state after sensing abnormal voltage. The board shuts down to prevent damage. This means the protection worked, and the board itself may be intact.
• A proper reset clears the protection flag and lets the board restart. Simply switching the breaker off and on is not always enough. Some boards need a specific timed sequence.
• Reading the error code history before condemning the PCB is key. It shows whether the fault is a one-time surge event or a pattern of board failure. A single surge code with no prior history points to lockout, not damage.