A9 on a Daikin Altherma HT: Malfunction of moving part of electronic expansion valve (Y1E)
Short answer
On a Daikin heat pump, A9 means: Malfunction of moving part of electronic expansion valve (Y1E). The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Malfunction of moving part of electronic expansion valve (Y1E).
Part involved: refrigerant circuit / pressure protection.
Likely causes:
- Malfunction of moving part of electronic expansion valve; Defect of indoor unit PC board (A1P); Defect of connecting cable, bad wire.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Resetting itself: unknown.
What you can check
- Read the full error code shown on the user interface and note it, with the date/time, for your installer.
- Look at the outdoor unit from outside: check the air inlet/outlet and fan grille are not blocked by leaves, debris, snow or heavy ice build-up (do not remove panels or touch the fan).
What the engineer will check
- Follow the service-manual troubleshooting flow chart for this code: check malfunction of moving part of electronic expansion valve; check defect of indoor unit PC board (A1P); check defect of connecting cable, bad wire.
Who to ask for: F-gas certified heat pump engineer (Daikin-trained installer / Stand By Me partner).
Certification: UK F-gas certification (Category I) for refrigerant circuit work; R-290 (Altherma 4) also needs flammable-refrigerant/hydrocarbon competence.
What you might notice
Sources
- Service Manual Daikin ALTHERMA HT ERSQ/ERRQ 011-016 AA V1/Y1 + EKHBRD (ESIE09-08C) ↗ · ESIE09-08C · page 148 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026