Mitsubishi Electric Mini-Split Lamp Lit Steady, Outdoor Unit Will Not Run
Hard lockoutShown as: Upper OPERATION INDICATOR lamp lights up solid (not blinking) while the outdoor unit does not operate
Outdoor control system error. The inverter or outdoor control board cannot read its nonvolatile memory, and the outdoor unit does not operate. The indoor lamp stays lit rather than blinking.
Manual wording: “Outdoor control system - Upper lamp lights up. Outdoor unit does not operate.”
Documented for: MSZ-GL and MSY-GL indoor units
Likely causes, most common first
- Defective inverter P.C. board
- Defective outdoor electronic control P.C. board
What you can safely check yourself
- Check that the breaker feeding the outdoor unit is on and not tripped
- Turn the system off at the breaker, wait one minute, and turn it back on once
When to call a technician
The manual's remedy is to read the LED blink pattern on the outdoor boards and replace the failed 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