A3 on a Fujitsu AIRSTAGE Monobloc Comfort: Compressor temperature protection
Short answer
On a Fujitsu heat pump, A3 means: Compressor temperature protection. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Compressor temperature protection.
Part involved: Compressor temperature protection.
Is it safe?
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: unknown.
Manual reset: unknown.
What you can check
- Note the error number shown after pressing the user interface. Check the heat pump breakers/isolators are on. Check the outdoor unit is not blocked by leaves, snow or ice (look only).
What the engineer will check
- Engineer diagnosis of outdoor monobloc unit (sensors, PCB/IPM, fan, compressor, refrigerant circuit - F-gas; water flow/circulator for AE/9B).
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.37 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026