Daikin AC-00 fault code
Daikin Altherma heat pumps
What it means
Booster heater overheated
The DHW booster heater overheated and its protection operated.
UK models this code applies to
From the Daikin service literature we hold (Daikin Altherma 3 M installer reference guide 4P685228-1B §14.4.2) — not a scraped list.
Altherma 3 M class 4 reversible (EBLA04E2V3)Altherma 3 M class 6 reversible (EBLA06E2V3)Altherma 3 M class 8 reversible (EBLA08E2V3)Altherma 3 M class 4 heating only (EDLA04E2V3)Altherma 3 M class 6 heating only (EDLA06E2V3)Altherma 3 M class 8 heating only (EDLA08E2V3)Altherma 3 M class 9 reversible (EBLA09D3V3)Altherma 3 M class 11 reversible (EBLA11D3V3)Altherma 3 M class 14 reversible (EBLA14D3V3)Altherma 3 M class 16 reversible (EBLA16D3V3)Altherma 3 M class 9 heating only (EDLA09D3V3)Altherma 3 M class 11 heating only (EDLA11D3V3)Altherma 3 M class 14 heating only (EDLA14D3V3)Altherma 3 M class 16 heating only (EDLA16D3V3)Altherma 3 M class 9 reversible 3-phase (EBLA09D3W1)Altherma 3 M class 11 reversible 3-phase (EBLA11D3W1)Altherma 3 M class 14 reversible 3-phase (EBLA14D3W1)Altherma 3 M class 16 reversible 3-phase (EBLA16D3W1)Altherma 3 M class 9 heating only 3-phase (EDLA09D3W1)Altherma 3 M class 11 heating only 3-phase (EDLA11D3W1)Altherma 3 M class 14 heating only 3-phase (EDLA14D3W1)Altherma 3 M class 16 heating only 3-phase (EDLA16D3W1)Altherma 4 H 4 kW R290 (EPSKS04A)Altherma 4 H 6 kW R290 (EPSKS06A)Altherma 4 H 7 kW R290 (EPSKS07A)
Now the harder half: proving what caused it
AC-00 names a symptom, not a root cause. In the app, the same code opens a guided investigation: what to measure first, the expected values for your exact model, and an honest verdict — including “nothing in this machine is broken” when that's what the readings say.
Chase this code in the app →