BoilerFaultCodesWhat the manual says
Manufacturer manualDHW mode ignition error
From this model's manual
Verified against the Vaillant Ecotec Pro Ecotec Plus System installation & service manual, page 59.
What causes this fault?
This fault occurs when the boiler detects that the burner is failing to light or stay lit specifically while trying to heat your domestic hot water. The most common reasons are a weak spark from worn-out ignition parts or a gas valve that isn't opening correctly to provide fuel. It can also be caused by moisture on the electrodes or a communication error within the core control board.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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