Mitsubishi Electric Mini-Split Code UD
Soft lockout
Overheat protection. The outdoor pipe thermistor TH3 or the condensing temperature from the high pressure sensor read 158F or more during compressor operation, so the unit stopped to protect itself.
Manual wording: “Overheat protection - Abnormal if outdoor pipe thermistor (TH3), condensing temperature T63HS detects 158F [70C] or more during compressor operation.”
Documented for: PUZ-HA and other A-Control outdoor units
Likely causes, most common first
- Defective outdoor fan (fan motor), or short cycle of the outdoor unit during cooling operation
- Defective outdoor pipe thermistor (TH3) or condensing temperature sensor
- Defective outdoor controller board
What you can safely check yourself
- Check that the outdoor unit is clear of snow, ice, leaves and stored items and has open air space around it
- Check that the outdoor fan is spinning when the unit runs
- Turn the system off at the breaker, wait one minute, and turn it back on once
When to call a technician
If the outdoor unit is clear and Ud returns, the fan motor or a sensor has failed. 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
- Service Manual No. OCH750 Revised Edition-E - PUZ-HA Outdoor Units (May 2024) (Mitsubishi Electric, PUZ-HA24NHA1, PUZ-HA30NKA, PUZ-HA36NKA, PUZ-HA42NKA1 heat-pump outdoor units) · checked 2026-08-25