Short answer: On many Mitsubishi indoor units, a fault shows as the Operation lamp blinking a set number of times, then pausing about 2.5 seconds. Count the blinks. Two blinks is a temperature sensor, three is the indoor fan, five is the outdoor power system. All of these are technician repairs. Your job is to count, write it down, and call.
How the blink code works
Mitsubishi Electric's service manual for its MSZ and MSY-GE series says to first check whether the Operation indicator lamp on the indoor unit is flashing on and off to signal a fault, and to count how many times it flashes before service starts.
When the unit reports a fault, the upper lamp flashes a number of times, then stays off for 2.5 seconds, then repeats. Watch two or three cycles so you count right.
This table comes from the manual for the MSZ-GE and MSY-GE NA models. Other Mitsubishi lines can differ, so check the label on your unit and your owner's manual.
| Upper lamp does this | What Mitsubishi says |
|---|---|
| Flashes quickly, 0.5 seconds on and 0.5 seconds off | Wiring or serial signal fault. The indoor unit has not received the outdoor unit's signal for 6 minutes and both units do not run |
| 2 flashes | Indoor coil or room temperature sensor is short or open |
| 3 flashes | Indoor fan motor. No rotation feedback signal during operation |
| 4 flashes | Indoor control system. The circuit board cannot read its memory |
| 5 flashes | Outdoor power system. The compressor stopped on overcurrent or start-up failure 3 times in a row within a minute of starting |
| 6 flashes | Outdoor temperature sensors short or open while the compressor runs |
| 7 flashes | Outdoor control system. The circuit board cannot read its memory |
| 14 flashes | An abnormality other than those above |
| Upper lamp stays lit, outdoor unit does not run | Outdoor control system. Check the board's LED pattern (technician) |
For multi-zone systems, the manual also lists a case where one lamp stays on and the other flashes. The cause is indoor units set to cool (or dry) and heat at once. The unit that was started first sets the mode, so set all units to the same mode.
What you can safely check
Stand where you can see the indoor unit's lamp, and count the blinks slowly, more than once. Then go through these steps.
- Count and write down the blinks. Also note the model number from the label.
- Check the remote. Mitsubishi's service manual says weak batteries cause remote problems. If the unit does not respond, replace the batteries first.
- Multi-zone systems: make sure every indoor unit is on the same mode.
- Look outside. Clear leaves and snow from around the outdoor unit, as long as it is off. A blocked unit can overheat. See mini split not cooling.
If a lamp is blinking, the unit has stopped itself for a reason. Do not keep switching it on and off.
When to call a technician
All of the numbered patterns above need a technician. Mitsubishi's remedies are things like replacing the circuit board, checking stop valves and checking the inverter or compressor, and its manual says to turn off the breaker before removing any panel. Do not do this yourself. Also call if a breaker trips or you see ice on the refrigerant lines.
Give the technician your model number and the number of blinks. That tells them which part to bring.
If the display shows "DF" instead of a fault, that is a normal defrost cycle. See what DF means on a mini split.
Related reading
- For what the remote symbols mean, see Mitsubishi remote symbols.
Sources
- Mitsubishi Electric service manual, MSZ-GE and MSY-GE NA series (OBH548D)
- Mitsubishi Electric operating instructions, MSZ/MSY-GL06 to GL15NA (battery and power safety notes)
Follow your unit's own manual. This is general information.
