E9 on a Daikin Altherma HT: Malfunction of moving part of electronic expansion valve (Y1E, Y3E)

What it means

The manual says: Malfunction of moving part of electronic expansion valve (Y1E, Y3E).

Part involved: refrigerant circuit / pressure protection.

When it shows: Error is generated under no common power supply when the power is on.

Likely causes:

• Defect of moving part of electronic expansion valve; Defect of outdoor unit PC board (A1P); Defect of connecting cable; Defect of indoor unit PC board (A4P).

Is it safe?

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 defect of moving part of electronic expansion valve; check defect of outdoor unit PC board (A1P); check defect of connecting cable; check defect of indoor unit PC board (A4P).

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

• No heating
• No hot water
• Keeps stopping / cutting out

Sources

• Service Manual Daikin ALTHERMA HT ERSQ/ERRQ 011-016 AA V1/Y1 + EKHBRD (ESIE09-08C) ↗ · ESIE09-08C · page 174 · Reviewed 23 September 2026

A code explains what the controller detected, not a confirmed root cause.

Reviewed: 23 September 2026