Vaillant aroTHERM F.526 fault code
Vaillant aroTHERM heat pumps
What it means
EEV outlet temperature sensor fault
The electronic expansion valve outlet temperature sensor is not connected, or is faulty.
Safety: Safe isolation before disconnecting sensors or working on the PCB.
UK models this code applies to
From the Vaillant service literature we hold (Vaillant hydraulic station installation & maintenance instructions 0020257319 (VWL 57…127/5 IS), fault-message table) — not a scraped list.
aroTHERM plus VWL 35/6aroTHERM plus VWL 55/6aroTHERM plus VWL 75/6aroTHERM plus VWL 105/6aroTHERM plus VWL 125/6
Now the harder half: proving what caused it
F.526 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 →