E1 on a Daikin heat pump: PC board defect
Short answer
On a Daikin heat pump, E1 means: PC board defect. 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: PC board defect.
Part involved: PCB / EEPROM.
When it shows: When data could not be correctly received from the E²PROM E²PROM: Type of nonvolatile memory. Mainta ins memory contents even when the power supply is turned off.
Likely causes:
- Defect of outdoor unit PC board (A1P); Defect compressor main PC board (A4P).
On the Altherma LT (low temperature split)
The manual says: Outdoor unit PCB abnormality.
Part involved: PCB / capacity setting.
When it shows: ■ When the programme of the microcomputer is in abnormal running order | When the programme of the microcomputer is in abnormal running order.
Likely causes:
- Out of control of microcomputer caused by external factors; Noise; Momentary fall of voltage; Momentary power loss; Defective outdoor unit PCB.
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? | 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.
- 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)
- Follow the service-manual troubleshooting flow chart for this code: check defect of outdoor unit PC board (A1P); check defect compressor main PC board (A4P).
Who to ask for: Heat pump engineer (Daikin-trained).
Certification: Electrical competence to BS 7671 for PCB replacement.
On the Altherma LT (low temperature split)
- Follow the service-manual troubleshooting flow chart for this code: check out of control of microcomputer caused by external factors; check noise; check momentary fall of voltage; check momentary power loss; check defective outdoor unit PCB.
Who to ask for: Heat pump engineer (Daikin-trained).
Certification: Electrical competence to BS 7671 for PCB replacement.
What you might notice
What owners and engineers report
2 owner and engineer reports mention this.
- No heating on the Altherma LT (low temperature split): 1 report
- Heat pump will not start 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 159 · Reviewed 23 September 2026
- Service Manual ALTHERMA ERHQ006~008BAV3 / ERLQ006~008BAV3(9) / EKHBH(X)008BA (ESIE10-02) ↗ · ESIE10-02 · page 158 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026