E6 on a Daikin heat pump: Standard compressor lock or over current
Short answer
On a Daikin heat pump, E6 means: Standard compressor lock or over current. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 2 sources
What it means
On the Altherma HT (high temperature split)
The manual says: Standard compressor lock or over current.
Part involved: compressor / inverter drive.
On the Altherma LT (low temperature split)
The manual says: Compressor lock.
Part involved: compressor / inverter drive.
When it shows: ■ Judging from current waveform generated when high-frequency voltage is applied to the compressor. ■ The system will be shut down if the error occurs 16 times. ■ Clearing condition: Continuous run for about 5 minutes (normal) | Judging from current waveform generated when high-frequency voltage is applied to the compressor. The system will be shut down if the error occurs 16 times. 3 3 Clearing condition: Continuous run for about 5 minutes (normal).
Likely causes:
- Compressor locked.
Is it safe?
On the Altherma HT (high temperature split)
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Resetting itself: unknown.
On the Altherma LT (low temperature split)
| 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: 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.
- Check the heat pump isolator switch(es) and the consumer-unit breaker/RCD for the heat pump are ON. If a breaker or RCD has tripped, do not keep resetting it - leave it and call an engineer.
What the engineer will check
On the Altherma HT (high temperature split)
- See Daikin service manual for this generation.
Who to ask for: F-gas certified heat pump engineer with electrical competence.
Certification: UK F-gas certification if the refrigerant circuit is opened; electrical competence (BS 7671) for inverter/PCB work.
On the Altherma LT (low temperature split)
- Follow the service-manual troubleshooting flow chart for this code: check compressor locked.
Who to ask for: F-gas certified heat pump engineer with electrical competence.
Certification: UK F-gas certification if the refrigerant circuit is opened; electrical competence (BS 7671) for inverter/PCB work.
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 Daikin ALTHERMA HT ERSQ/ERRQ 011-016 AA V1/Y1 + EKHBRD (ESIE09-08C) ↗ · ESIE09-08C · page 141 · Reviewed 23 September 2026
- Service Manual ALTHERMA ERHQ006~008BAV3 / ERLQ006~008BAV3(9) / EKHBH(X)008BA (ESIE10-02) ↗ · ESIE10-02 · page 161 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026