Mitsubishi Electric Mini-Split Code UL
Soft lockout
Abnormal low pressure. Three minutes after the compressor started, the temperature difference TH32 minus TH4 was 68F or more and TH32 exceeded 176F, which the control reads as a low pressure condition.
Manual wording: “Abnormal low pressure - Abnormal if TH32-TH4 is 68F [20C] or higher and TH32 exceeds 176F [80C] after compressor starts operating for 3 minutes.”
Documented for: PUZ-HA and other A-Control outdoor units
Likely causes, most common first
- Stop valve of the outdoor unit is closed during operation
- Leakage or shortage of refrigerant
- Malfunction of the linear expansion valve
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
The manual's remedies are to check the stop valve, correct the refrigerant charge and check the expansion valve. All of that is a technician job.
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