What the manual says
Manufacturer manualHeat exchanger antifreeze active, as fan speed variation is too high. Appliance is within the waiting time of the operation block function
From this model's manual
Verified against the Vaillant/Vaillant Ecotec Plus 612 4104460 installation & service manual, page 43.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Related fault codes
All 77 fault codes on the ecoTEC
Seeing a different code? Every code this model can display, in one place.
Communication faultD.17F.00F.01F.02F.03F.10F.11F.12F.13F.20F.22F.23F.24F.25F.26F.27F.28F.29F.32F.35F.42F.49F.52F.53F.54F.56F.57F.61F.62F.63F.64F.65F.67F.68F.70F.71F.72F.73F.74F.75F.76F.77F.78F.83F.84F.85F.91F.92F.93S.10S.11S.13S.14S.15S.16S.17S.20S.21S.22S.23S.24S.25S.26S.27S.28S.30S.31S.34S.41S.42S.53S.54S.96S.97S.98