A6 on a Daikin Altherma HT: Pump error
Short answer
On a Daikin heat pump, A6 means: Pump error. 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: Pump error.
Part involved: water flow / circulation pump / flow sensor.
When it shows: When number of turns cannot be detected even when output voltage to the pump motor is maximum. When water sensors are not within expected range.
Likely causes:
- Pump rotor locked; Disconnected or faulty wiring between pump connector and PC board (A1P); Blocked waterflow or heat exchanger (waterside).
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.
- Check the heating-system water pressure reading on the gauge/display: Daikin operation manuals ask users to check it is above 1 bar. If it is below that, report it to your installer (do not open the unit).
What the engineer will check
- Follow the service-manual troubleshooting flow chart for this code: check pump rotor locked; check disconnected or faulty wiring between pump connector and PC board (A1P); check blocked waterflow or heat exchanger (waterside).
Who to ask for: Heat pump installer / heating engineer.
Certification: None specific for water-side checks; MCS-certified installer recommended.
What you might notice
Sources
- Service Manual Daikin ALTHERMA HT ERSQ/ERRQ 011-016 AA V1/Y1 + EKHBRD (ESIE09-08C) ↗ · ESIE09-08C · page 147 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026