Mitsubishi Ecodan L4 fault code
Mitsubishi Ecodan heat pumps
What it means
DHW tank overheat protection (THW5 ≥75 °C)
THW5 reads ≥75 °C for 10 consecutive seconds.
UK models this code applies to
From the Mitsubishi Electric service literature we hold (Ecodan FTC service manual, error-code chapter + §10-6 thermistor tables) — not a scraped list.
Ecodan PUZ-WM50VHA (R32)Ecodan PUZ-WM60VAA (R32)Ecodan PUZ-WM85VAA (R32)Ecodan PUZ-WM85YAA 3-phase (R32)Ecodan PUZ-WM112VAA (R32)Ecodan PUZ-WM112YAA 3-phase (R32)Ecodan PUZ-WZ50VAA (R290)Ecodan PUZ-WZ60VAA (R290)Ecodan PUZ-WZ85VAA (R290)Ecodan PUZ-WZ85YAA 3-phase (R290)Ecodan PUZ-WZ100VAA (R290)Ecodan PUZ-WZ100YAA 3-phase (R290)Ecodan PUZ-WZ120VAA (R290)Ecodan PUZ-WZ120YAA 3-phase (R290)
Now the harder half: proving what caused it
L4 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 →