Daikin L4-00 fault code
Daikin Altherma heat pumps
What it means
OU: Malfunction of inverter radiating fin temperature rise
The inverter heat sink is too hot. The drive throttles or stops to protect itself.
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
L4-00 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 →