Heat pumps · Error codes · Hitachi
F12Hitachi · Yutaki M (RHUE, 1st generation)
F12 on a Hitachi Yutaki M: Heat pump fault
Short answer
On a Hitachi heat pump, F12 means: Heat pump fault. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Heat pump fault.
Part involved: ATW-CPA-02 advanced system controller.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: yes - when condition clears.
What you can check
- Read and note the alarm code and any retry code (e.g. P70) shown on the unit controller.
- Check the heat pump supply breaker/isolator at the consumer unit is ON.
- Restart once via the unit controller (or switch off/on at the isolator) - the manual states the unit must be stopped to release most alarms; if the code returns, call an engineer.
- Check the system pressure gauge on the indoor unit (Yutaki S / S Combi have a factory manometer; Yutaki M uses a field-fitted gauge) - Hitachi gives about 1.5-2.0 bar as normal and it must stay above 1 bar and below 3 bar.
- Check the filling loop is closed.
What the engineer will check
- Check system sensors, valve operation and heat pump alarm on 7-segment display.
Who to ask for: Heating engineer / MCS heat pump installer.
What you might notice
Sources
- YUTAKI M Series RHUE-3AVHN1 / RHUE-(3-6)A(V)HN-HM Technical Catalogue ↗ · TCGB0090 rev.0 - 12/2013 · page p.140-141 (PDF p.148-149) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026