89-06 on a Daikin Altherma: Heat exchanger freeze-up protection activated during cooling operation. (warning)
Short answer
On a Daikin heat pump, 89-06 means: Heat exchanger freeze-up protection activated during cooling operation. (warning). 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: Heat exchanger freeze-up protection activated during cooling operation. (warning).
Part involved: plate heat exchanger freeze protection.
When it shows: Water heat exchange freezing abnormality during cooling. Outlet water temperature <5°C or 1.5°C (glycol) for 5 seconds OR saturated evaporation temperature (pressure sensor) <−11°C for 5 minutes from start of cooling. At second occurrence, error 89‑05 is triggered.
Likely causes:
- Water flow is too low.; Faulty refrigerant pressure sensor.; Faulty outlet water after heat exchanger thermistor.; Refrigerant overcharge or shortage.; Clogged refrigerant circuit.; Non‑condensables and/or humidity in the refrigerant circuit.; Faulty hydro PCB.
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running.
Resetting itself: unknown.
Manual reset: Auto reset.
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 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).
- 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).
- 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
- seconds OR saturated evaporation temperature (pressure sensor) <−11°C for 5 minutes from start of cooling. At second occurrence, error 89‑05 is triggered. Unit will stop operating. Auto reset. ; | Troubleshooting ; Check the water flow. . ; Perform a check of the refrigerant pressure sensor. . ; Perform a check of the outlet water after heat exchanger thermistor. . ; Check if the refrigerant circuit is correctly charged. . ; Check if the refrigerant circuit is clogged. . ; Check for the presence of non‑condensables and/or humidity in the refrigerant circuit. . ; Perform a check of the hydro PCB. .
Who to ask for: Heat pump installer / heating engineer.
Certification: None specific for water-side checks; MCS-certified installer recommended.
What you might notice
What owners and engineers report
14 owner and engineer reports mention this.
- No heating on the Altherma: 7 reports
- Keeps stopping / cutting out on the Altherma: 2 reports
- No hot water on the Altherma: 2 reports
- Stops working in very cold weather on the Altherma: 2 reports
- Frequent defrosting on the Altherma: 1 report
Sources
- Service manual Daikin Altherma 3 M EBLA/EDLA04~08E (ESIE22-09) ↗ · ESIE22-09 · page 28 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026