Mitsubishi Electric Mini-Split 4 Blinks
Hard lockoutShown as: Upper OPERATION INDICATOR lamp blinks 4 times, then 2.5 seconds off, repeating
Indoor control system error. The indoor electronic control board cannot read its own nonvolatile memory correctly.
Manual wording: “Indoor control system - It cannot properly read data in the nonvolatile memory of the indoor electronic control P.C. board.”
Documented for: MSZ-GL and MSY-GL indoor units
Likely causes, most common first
- Defective indoor electronic control P.C. 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 electronic control P.C. 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.
Source
- Indoor Unit Service Manual No. OBH732 Revised Edition-D - MSZ-GL/MSY-GL Series (Mitsubishi Electric, MSZ-GL06NA/GL09NA/GL12NA/GL15NA/GL18NA/GL24NA and MSY-GL09NA/GL12NA/GL15NA/GL18NA/GL24NA wall-mounted indoor units) · checked 2026-08-25