BoilerFaultCodesWhat the manual says
Manufacturer manualNo demand to gas valve | Electronic board defective; Gas valve defective
From this model's manual
Verified against the Vaillant Turbomax Plus 824 828e installation & service manual, page 40.
What causes this fault?
This fault occurs when the boiler's sensors detect a flame signal even though the gas valve should be closed and no heating is requested. The most common reason is a leaking gas valve allowing fuel to seep through, or a faulty circuit board that is incorrectly interpreting electrical signals as a flame.
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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