10 on a Fujitsu heat pump: Communication error with controller board
Short answer
On a Fujitsu heat pump, 10 means: Communication error with controller board. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 2 sources
What it means
On the AIRSTAGE Monobloc Comfort (R32)
The manual says: Communication error with controller board.
Part involved: Communication error with controller board.
Likely causes:
- Loss of connection between controller and display.
On the WATERSTAGE split (Comfort, High Power, Super High Power)
The manual says: Outdoor sensor.
Part involved: sensor/controller: BX4 / X84 (B9).
Likely causes:
- Short-circuit; unplugged or disconnected sensor; faulty sensor; other fault.
Is it safe?
On the AIRSTAGE Monobloc Comfort (R32)
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Resetting itself: unknown.
Manual reset: unknown.
On the WATERSTAGE split (Comfort, High Power, Super High Power)
| 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: no.
Manual reset: no.
What you can check
On the AIRSTAGE Monobloc Comfort (R32)
- Note the error number shown after pressing the user interface. Check the heat pump breakers/isolators are on.
On the WATERSTAGE split (Comfort, High Power, Super High Power)
- Note the error number shown after pressing the Info (i) key on the Waterstage user interface. Check the heat pump breakers/isolators are on. The user manual RESET key/'Reset HP' is for installers ('do not use during normal operation') - contact your installer if the fault remains.
What the engineer will check
On the AIRSTAGE Monobloc Comfort (R32)
- Check wiring between T24 and display.
Who to ask for: Heat pump / refrigeration engineer (manufacturer-trained).
Certification: F-gas certification for refrigerant-circuit work; electrical competence (Part P/18th Edition) for PCB/wiring.
On the WATERSTAGE split (Comfort, High Power, Super High Power)
- Check the sensor's wiring; replace the sensor.
Who to ask for: Heat pump / refrigeration engineer (manufacturer-trained).
Certification: F-gas certification for refrigerant-circuit work; electrical competence (Part P/18th Edition) for PCB/wiring.
What you might notice
Sources
- INSTALLATION - General Monobloc Comfort Duo, Monobloc 2 services air/water heat pump ↗ · U0780597_2690_EN_3 · page p.36 · Reviewed 23 September 2026
- Maintenance Document - Air to Water Heat Pump Split single service and integrated DHW type (Super High Power) ↗ · 2105_EN_1 · page SHP SM p.5; DTM p.110; SHP IM p.74 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026