E5-00 on a Daikin Altherma: OU: Overheat of inverter compressor motor
Short answer
On a Daikin heat pump, E5-00 means: OU: Overheat of inverter compressor motor. The heat pump keeps running. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: OU: Overheat of inverter compressor motor.
Part involved: compressor / inverter drive.
When it shows: Compressor overload is detected.
Likely causes:
- Closed stop valve in the refrigerant circuit.; Faulty discharge pipe thermistor or connector fault.; Faulty outdoor unit fan motor.; Faulty compressor or miswiring of the compressor power supply cable.; Faulty expansion valve.; Faulty 4‑way valve.; Faulty main PCB.; Refrigerant shortage.; Non‑condensables and/or humidity in the refrigerant circuit.; Clogged refrigerant circuit.
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running.
Resetting itself: yes.
Manual reset: Automatic reset if the unit runs without warning for 60 seconds.
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.
- 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.
- Daikin documents this code as resetting automatically once the condition clears; if it keeps coming back, contact your installer.
- 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
- Check that all stop valves of the refrigerant circuit are open. . ; Perform a check of the discharge pipe thermistor. . ; Perform a check of the outdoor unit fan motor. . ; Perform a check of the compressor. . ; Perform a check of the expansion valve. . ; Perform a check of the 4‑way valve. . ; Perform a check of the main PCB. . ; Check if the refrigerant circuit is correctly charged. . ; Check for the presence of non‑condensables and/or humidity in the refrigerant circuit. . ; Check if the refrigerant circuit is clogged. . ; | Troubleshooting.
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
11 owner and engineer reports mention this.
- No heating on the Altherma: 7 reports
- Keeps stopping / cutting out on the Altherma: 2 reports
- Unusual noise on the Altherma: 2 reports
Sources
- Service manual Daikin Altherma 3 M EBLA/EDLA04~08E (ESIE22-09) ↗ · ESIE22-09 · page 45 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026