BoilerFaultCodesYour boiler’s computer is confused about which specific model it is supposed to be, usually happening after a major part has been replaced.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: DSN appliance variant setting
What causes this fault?
This fault occurs when the boiler's main control board has lost its identity and doesn't know which power output or model size it is controlling. It most frequently happens after a new circuit board has been installed but hasn't been programmed with the correct device specific number. Without this data, the boiler stays in a safety mode because it doesn't know how much gas to burn or how fast to run the internal components.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like D.93 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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