Mitsubishi Electric Mini-Split Code U7
Soft lockout
Too low superheat due to low discharge temperature. Discharge superheat stayed at 5F or below for 3 minutes even with the linear expansion valve at its minimum opening, meaning liquid refrigerant is likely reaching the compressor.
Manual wording: “Too low superheat due to low discharge temperature - Abnormal if discharge superheat is continuously detected less than or equal to 5F [-15C] for 3 minutes”
Documented for: A-Control outdoor units (PUZ, MUZ, MXZ)
Likely causes, most common first
- Disconnection or loose connection of the discharge temperature thermistor (TH4)
- Defective high pressure or temperature sensing
- Disconnection or loose connection of the linear expansion valve or its connector
- Defective linear expansion valve
- Overcharge of refrigerant
What you can safely check yourself
- Turn the system off at the breaker, wait one minute, and turn it back on once
When to call a technician
Expansion valve and refrigerant charge problems require gauges and EPA certification. 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