Mitsubishi Electric MSZ-GL / MSY-GL Error Codes
Mitsubishi indoor units show faults by blinking the OPERATION INDICATOR lamp. These counts are from the failure mode recall table; the blink counts during a live fault can differ, and outdoor details need the outdoor unit's service manual.
| Code | Meaning | What to check |
|---|---|---|
| Not lit | Normal. | |
| 1 blink (0.5 s) | Room temperature thermistor short or open. | Measure against the thermistor chart in the service manual. How to fix → |
| 2 blinks | Indoor coil thermistor short or open. | Measure against the thermistor chart. How to fix → |
| 3 blinks | Serial signal: no signal from the outdoor unit for up to 6 minutes. | Miswiring, interconnect wiring, outdoor power. How to fix → |
| 11 blinks | Indoor fan motor: no rotation feedback 12 seconds after start. | Fan motor, connector, wheel binding. |
| 12 blinks | Indoor control system: nonvolatile memory can't be read. | Replace the indoor electronic control board. |
How to read the codes
- Count the blinks between the 2.5-second OFF pauses, and watch at least two cycles.
- Failure mode recall reads the stored indoor fault even if it isn't happening now. The procedure is in the indoor unit service manual.
- If recall shows the outdoor unit is at fault, use the outdoor unit's failure mode recall and LED table.
Source: Mitsubishi Electric MSZ-GL/MSY-GL Indoor Unit Service Manual OBH732, Indoor unit failure mode table. The "meaning" column follows the manufacturer's wording; "what to check" is our field summary. Always go by the label on the furnace you're working on.
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