Fb - The indoor unit control system has detected a memory or control fault.
Mitsubishi Electric lists Fb as an indoor unit control system error, with the note 'memory error, etc.' in the PEA installation manual. This points to an internal electronics or control-board issue inside the indoor unit.
Applies to the PEA-M100-160HAA installation-manual family; controller presentation may vary slightly by installation.
Severity
High
Display
Shown as check code Fb on the remote controller. In the self-check table, twelve beeps/flashes map to Fb.
Support first?
Often not
Models in range
PEA-M100HAA, PEA-M125HAA, PEA-M140HAA
What to do first
Start with these checks
- 1Turn the system off and restart it once after a short wait.
- 2If Fb returns, leave the unit off and arrange service.
- 3Avoid repeated resets if the code keeps coming back.
Likely causes
What usually sits behind this code
Indoor control-board fault
Memory or internal control-system error
Power-quality or wiring issue affecting the indoor controller
Contact support
Contact customer support if any of these apply
- !Fb reappears after restart
- !The controller cannot operate the unit normally
- !Other control-related faults appear alongside Fb
- - The official table labels Fb as 'Indoor unit control system error (memory error, etc.)'.
- - Because the code points to internal controls, field repair usually needs trained service access.
Related codes
Nearby codes in this family
More ranges
More Mitsubishi Electric air-conditioner ranges
Source notes
Source and scope
Source: Mitsubishi Electric Australia installation manual
The PEA-M100-160HAA installation manual lists Fb as 'Indoor unit control system error (memory error, etc.)'.
Last reviewed: 2026-04-19
This meaning comes directly from Mitsubishi Electric's official code table, but internal control faults still require qualified diagnosis and repair.