BoilerFaultCodesYour boiler has detected an error with its internal temperature settings or the control unit, which may cause it to stop providing heating or hot water correctly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Set temperature adjustable from 1 to 127°C
What causes this fault?
This fault occurs when the boiler's internal computer receives conflicting or impossible data regarding the temperatures it is supposed to maintain. It is usually caused by a communication failure between the main control board and the electronic coding plug that stores the boiler's specific settings. In some cases, damaged internal wiring or a failing circuit board can also lead to these incorrect readings.
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.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like 9b:1 to 9b:127 — 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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