Mitsubishi Electric Mini-Split Code FB
Hard lockout
Indoor unit control system error. Data cannot be read normally from the nonvolatile memory of the indoor controller board.
Manual wording: “Indoor controller board - Abnormal if data cannot be read normally from the nonvolatile memory of the indoor controller board.”
Documented for: A-Control indoor units
Likely causes, most common first
- Defective indoor controller board
What you can safely check yourself
- Turn the system off at the breaker, wait one minute, and turn it back on once
When to call a technician
The manual's only remedy is to replace the indoor controller board. Call a technician.
A Mitsubishi Electric mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- Indoor Unit Service Manual No. OCH761 Revised Edition-A - PKA-A LA Series (May 2021) (Mitsubishi Electric, PKA-A12LA, PKA-A18LA, PKA-A12LA.TH, PKA-A18LA.TH wall-mounted indoor units) · checked 2026-08-25
- Service Manual No. OCH750 Revised Edition-E - PUZ-HA Outdoor Units (May 2024) (Mitsubishi Electric, PUZ-HA24NHA1, PUZ-HA30NKA, PUZ-HA36NKA, PUZ-HA42NKA1 heat-pump outdoor units) · checked 2026-08-25