Ed
Serial Communication Error (Outdoor Unit Internal)
Mitsubishi Electric · PAR-21MAA MA Remote Controller
What does Ed mean?
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.
Repair Steps
- 1
Physically check if connector (CN4) between the outdoor controller board and outdoor power board is disconnected.
- 2
Inspect connectors (CNMNT and CNVMNT) on the outdoor controller board for poor connections.
- 3
Cycle power to the unit (turn off, then on again) to re-check for the error.
Verified technical data. Last updated: March 2026
Source: Mitsubishi Electric PAR-21MAA MA Remote Controller