Backup heater overheated or BUH power cable not connected
Daikin group two very different things under one code: the backup heater overheated, OR its power cable is not connected at all. Check the cable first — it is the quicker of the two to eliminate.
How to read it — controller display: Altherma error codes show directly on the user interface / main controller display — no button dance needed. (Daikin Altherma 3 M installer reference guide, §14.4.2 error-code table)
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)Altherma HT ERSQ011AAV1Altherma HT ERSQ011AAY1Altherma HT ERSQ014AAV1Altherma HT ERSQ014AAY1Altherma HT ERSQ016AAV1Altherma HT ERSQ016AAY1Altherma HT ERRQ011AAV1Altherma HT ERRQ011AAY1Altherma HT ERRQ014AAV1Altherma HT ERRQ014AAY1Altherma HT ERRQ016AAV1Altherma HT ERRQ016AAY1Altherma LT split ERHQ011BV3Altherma LT split ERHQ014BV3Altherma LT split ERHQ016BV3Altherma LT split ERHQ011BW1Altherma LT split ERHQ014BW1Altherma LT split ERHQ016BW1Altherma LT split ERLQ004CAV3Altherma LT split ERLQ006CAV3Altherma LT split ERLQ008CAV3Altherma LT split ERLQ011CAV3Altherma LT split ERLQ014CAV3Altherma LT split ERLQ016CAV3Altherma LT split ERLQ011CAW1Altherma LT split ERLQ014CAW1Altherma LT split ERLQ016CAW1Altherma 3 R split ERLA11DV3Altherma 3 R split ERLA14DV3Altherma 3 R split ERLA16DV3Altherma 3 R split ERLA11DW1Altherma 3 R split ERLA14DW1Altherma 3 R split ERLA16DW1Altherma 3 H HT split EPRA14DAV3Altherma 3 H HT split EPRA16DAV3Altherma 3 H HT split EPRA18DAV3Altherma 3 H HT split EPRA14DAW1Altherma 3 H HT split EPRA16DAW1Altherma 3 H HT split EPRA18DAW1Altherma LT monobloc EDLQ05CAV3Altherma LT monobloc EDLQ07CAV3Altherma LT monobloc EBLQ05CAV3Altherma LT monobloc EBLQ07CAV3Altherma 3 R split 4-8 kW ERGA04EVAltherma 3 R split 4-8 kW ERGA06EVAltherma 3 R split 4-8 kW ERGA08EV
Now the harder half: proving what caused it
AA-01 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.