BoilerFaultCodesYour boiler is simply letting you know that it is due for its routine annual service soon.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical description: Maintenance indicator – number of hours until the next maintenance
What causes this fault?
This code is triggered because your boiler has a built-in timer or run-hour counter that tracks how long it has been since its last professional inspection. It is not a mechanical failure but rather a proactive reminder set by an engineer to ensure the appliance remains safe and efficient. Once the pre-set time limit is reached, the system displays this notification to nudge you to book your annual maintenance.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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A boiler cover plan would cover faults like D.84 — no call-out fees, no surprises.
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