BoilerFaultCodesYour boiler has detected an issue with its internal combustion levels and cannot regulate the gas flame safely.
Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now — this fault can be dangerous if ignored.
Technical description: Current values reached – check combustion values and CO2 calibration, try resetting the boiler if this fails. Either the board or the valve will need replacing.
What causes this fault?
This fault occurs when the boiler's internal sensors detect that the gas and air mixture is no longer burning within safe, controlled limits. It usually happens because the gas valve is failing to regulate the flow correctly or the main control board has lost the ability to calibrate the flame, leading the system to shut down for safety.
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 E77 — 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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