Vaillant VU 446/5-5 / VU 606/5-5 fault codes

30 codes from the Vaillant manual for the VU 446/5-5 / VU 606/5-5 gas boiler. Pick one for what it means, the likely causes and where to start.

Code	What it means
F.00	Flow temperature sensor interruption
F.01	Return temperature sensor interruption
F.03	Cylinder temperature sensor interruption
F.10	Flow temperature sensor short circuit
F.11	Return temperature sensor short circuit
F.13	Cylinder temperature sensor short circuit
F.22	Safety shutdown: water deficiency
F.23	Safety shutdown: temperature spread too great
F.24	Safety shutdown: temperature rise too fast
F.25	Safety shutdown: flue gas temperature too high
F.27	Safety shutdown: flame simulation
F.32	Fan fault
F.33	Air pressure switch fault
F.64	Fault: electronics/NTC
F.65	Electronics temperature fault
F.72	Flow and/or return temperature sensor fault
F.74	Water pressure sensor signal outside correct range (too high)
F.75	Pump fault/water deficiency
F.77	Accessory fault (flue non-return flap, condensate pump, etc.)
F.83	Flow and/or return temperature sensor temperature change fault
F.84	Temperature difference fault at the flow and return temperature sensors
F.85	Flow and return temperature sensors installed incorrectly (inverted)
P.02	Minimum load check programme
S.42	Flue non-return flap closed
S.46	Comfort protection: minimum load, loss of flame
S.53	Waiting time: water shortage
S.54	Waiting time: water shortage
S.62	Adjust CO2
S.85	Service message: check water circulation volume
S.93	Flue gas measurement not possible