What U8 means
The outdoor unit fan protection stopped the unit.
Also shown as: 8 blinks outdoor, depending on the model.
Likely causes
- Outdoor fan blocked by ice, snow or debris
- Fan motor fault
Safe first checks
- Turn the system off at the breaker and check that the outdoor fan isn't blocked by snow, ice or debris. Don't reach into the fan.
When to stop
If U8 returns, call an HVAC technician.
Checked against: Mitsubishi Electric, Mr. Slim indoor/outdoor unit malfunction-diagnosis check codes (2024-11-18). Codes can differ by model and year, so confirm with your owner's manual.