Mitsubishi Electric U1 Error Code: Abnormal high pressure or overheating protection
Updated October 2026 · Sourced from Mitsubishi Electric documentation
🛑 Turn it off and call a licensed pro
The outdoor side reports abnormal high pressure (63H operated) or overheating protection operation. The manual lists U1 and Ud together.
Is it safe to keep running? No. Turn it off and get it checked. Turn the unit off and call a licensed technician.
U1 at a glance
| Code / how it shows | Meaning | Applies to |
|---|---|---|
| U1 Also: Ud Second self-check pattern, 6 flashes | Abnormal high pressure or overheating protection | PLA-RP35/50/60/71/100/125/140BA ceiling cassette indoor units (Mr. Slim, OCH416 service manual) |
🛑 Stop and call a licensed pro if
- Turn the unit off and call a licensed technician.
- Any code pointing to refrigerant, the compressor, high pressure or the outdoor unit board. Refrigerant work legally needs a certified technician.
- Burning smell, sparks, or a breaker that trips again after a reset.
- Water leaking from the indoor unit that does not stop after the drain is clear.
Safe first steps for any Mitsubishi Electric code
- Write down the exact code and how it shows (remote display or number of lamp blinks). Similar codes mean different things on different series.
- Turn the system off at the remote, switch off the breaker or disconnect for the unit, wait a few minutes, then turn it back on.
- Clean or replace the indoor unit air filters, and make sure nothing blocks the indoor or outdoor unit.
- Check that the condensate drain line is not blocked or kinked where you can see it.
- Replace the remote controller batteries if the display is dim or the unit does not respond.
Source: Mitsubishi Electric PLA-RP BA Service Manual OCH416 Rev. D, p.22. Codes are series-specific, so your unit's own manual is the final word. Reviewed October 2026.
Shaun Cain · Certified HVAC & Refrigeration Technician · Ask an HVAC technician
Related Mitsubishi Electric codes
P1 : Intake (room) sensor errorP2 : Pipe (liquid) sensor errorP9 : Pipe (condenser/evaporator) sensor errorE6 : Indoor/outdoor unit communication errorP4 : Float switch connector openP5 : Drain pump error (water leakage abnormality)PA : Forced compressor stopP6 : Freezing or overheating protection operationEE : Communication error between indoor and outdoor unitsP8 : Pipe temperature errorE4 : Remote controller signal receiving errorFb : Indoor unit control system error