EA on a Daikin Altherma LT: Heating / Cooling switching failure
Short answer
On a Daikin heat pump, EA means: Heating / Cooling switching failure. 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: Heating / Cooling switching failure.
Part involved: refrigerant circuit / pressure protection.
When it shows: A following condition continues over 10 minute after operating 5 minutes. ■ Cooling (Outlet water temperature – hydro-box heat exchanger temperature) < -10°C ■ Heating (Hydro-box heat exchanger temperature – Outlet water temperature) < -10°C | A following condition continues over 10 minute after operating 5 minutes. Cooling (Outlet water temperature – hydro-box heat exchanger temperature) < -10°C 3 3 Heating (Hydro-box heat exchanger temperature – Outlet water temperature) < -10°C.
Likely causes:
- Connector in poor contact; Thermistor defective; Outdoor unit PCB defective; Four way valve coil or harness defective; Four way valve defective; Foreign substance mixed in refrigerant; Insufficient gas.
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.
Manual reset: Reset via the remote controller (Inspection/Test button) after the cause is fixed; some codes need a manual reset of the remote-controller memory (service manual section 1.4).
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 connector in poor contact; check thermistor defective; check outdoor unit PCB defective; check four way valve coil or harness defective; check four way valve defective; check foreign substance mixed in refrigerant.
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
1 owner and engineer report mentions this.
- No heating on the Altherma LT (low temperature split): 1 report
Sources
- Service Manual ALTHERMA ERHQ006~008BAV3 / ERLQ006~008BAV3(9) / EKHBH(X)008BA (ESIE10-02) ↗ · ESIE10-02 · page 165 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026