BoilerFaultCodesWhat the manual says
Manufacturer manualError with gas valve – switch off delay
From this model's manual
Verified against the Vaillant/Vaillant Ecotec Plus 637 4104465 installation & service manual, page 47.
What causes this fault?
This fault occurs when the boiler's control system detects that the gas flame is still burning even after it has told the gas valve to close. The most common reason is a mechanical failure within the gas valve itself, but it can also be caused by a faulty circuit board incorrectly sensing a flame that isn't actually there.
Engineer required
This is a emergency severity fault. Stop using the boiler and call 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 plus 637
Seeing a different code? Every code this model can display, in one place.
Communication faultd.71F.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.63F.64F.65F.67F.68F.70F.71F.72F.73F.74F.75F.76F.77F.78F.83F.84F.85F.91F.92F.93S.04S.10S.11S.14S.15S.16S.17S.20S.21S.22S.23S.24S.25S.26S.27S.28S.30S.31S.32S.34S.41S.42S.53S.54S.96S.97S.98