E9-00 on a Daikin Altherma: Malfunction of electronic expansion valve
Short answer
On a Daikin heat pump, E9-00 means: Malfunction of electronic expansion valve. 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: Malfunction of electronic expansion valve.
Part involved: refrigerant circuit / pressure protection.
When it shows: No continuity of the expansion valve. Minimum expansion valve opening and suction superheat <4 K and discharge superheat <5 K.
Likely causes:
- Faulty refrigerant side thermistor(s).; Faulty expansion valve.; Closed stop valve in the refrigerant circuit.; Clogged refrigerant circuit.; Refrigerant overcharge.; Non‑condensables and/or humidity in the refrigerant circuit.; Faulty main PCB.; ▪ Faulty or disturbance of the power supply (power supply MUST be within range of nominal operating voltage ±4%), ▪ Power drop, ▪ Short circuit.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: no.
Manual reset: Manual reset via user interface. Power reset via outdoor unit.
What you can check
- Read the full error code and sub-code shown on the user interface (Malfunctioning screen; press the help button for Daikin's long description) 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).
- Do NOT bleed radiators while an error/malfunction symbol is displayed: Daikin operation manuals warn refrigerant may have leaked into the water circuit - ventilate and call your installer.
- If heating/hot water has stopped, the operation manual lets the user confirm on the Malfunctioning screen whether the backup/booster heater may take over as emergency heating (much higher running cost) until the installer attends.
What the engineer will check
- Perform a check of all refrigerant side thermistors. . ; Perform a check of the expansion valve. . ; Check that all stop valves of the refrigerant circuit are open. . ; Check if the refrigerant circuit is clogged. . ; Check if the refrigerant circuit is correctly charged. . ; Check for the presence of non‑condensables and/or humidity in the refrigerant circuit. . ; Perform a check of the main PCB. . ; Check if the power supply is compliant with the regulations. . ; | Troubleshooting.
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
What owners and engineers report
11 owner and engineer reports mention this.
- No heating on the Altherma: 7 reports
- Keeps stopping / cutting out on the Altherma: 2 reports
- No hot water on the Altherma: 2 reports
Sources
- Service manual Daikin Altherma 3 M EBLA/EDLA04~08E (ESIE22-09) ↗ · ESIE22-09 · page 48 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026