Mitsubishi Electric · PAR-21MAA MA Remote Controller
A serial communication error has occurred either between the outdoor controller board and the outdoor power board, or between the outdoor controller board and the M-NET P.C. board. This critical internal error prevents components within the outdoor unit from communicating correctly, leading to system failure.
Click steps to track your progress.
Physically check if connector (CN4) between the outdoor controller board and outdoor power board is disconnected.
Inspect connectors (CNMNT and CNVMNT) on the outdoor controller board for poor connections.
Cycle power to the unit (turn off, then on again) to re-check for the error.