Mitsubishi Air Conditioner Error Code Er2

Er2 indicates a write error caused by an attempt to modify inverter parameters while the unit is running and Pr.77 is set to 0. This setting blocks parameter changes during active operation as a protection measure. The error is procedural, not a sign of hardware failure. Stopping the inverter before writing parameters will resolve the issue.

A reset may clear the displayed error code, but Er2 will return immediately if the same parameter write is attempted again while the inverter is running. The underlying cause, a write command being sent during operation, must be corrected. Simply resetting without addressing the procedure or Pr.77 configuration will not provide a lasting fix.

Because Er2 is a configuration or procedural error rather than a parts failure, repair costs are typically limited to labor charges for a technician to diagnose and correct the parameter write sequence or Pr.77 setting. Expect service call fees in the range of 75 to 200 dollars depending on your location and the technician's time on site. No replacement parts are needed in most cases.

Stop the inverter completely before attempting any parameter write operations. Once the unit is fully stopped, the write command can be executed without triggering Er2. If parameter writes during operation are required for your application, review the Pr.77 setting to determine whether it can be adjusted to permit writes while running.

Er2 itself does not indicate a dangerous condition or component failure. It is a protective response that prevents the inverter from accepting potentially disruptive setting changes while it is actively running. The unit is functioning as designed when it generates this error. Address the write procedure and the unit will continue normal operation.